Cancer

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This article is about the group of diseases. Cancer_sentence_0

For other uses, see Cancer (disambiguation). Cancer_sentence_1

Cancer_table_infobox_0

CancerCancer_header_cell_0_0_0
Other namesCancer_header_cell_0_1_0 Malignant tumor, malignant neoplasmCancer_cell_0_1_1
PronunciationCancer_header_cell_0_2_0 Cancer_cell_0_2_1
SpecialtyCancer_header_cell_0_3_0 OncologyCancer_cell_0_3_1
SymptomsCancer_header_cell_0_4_0 Lump, abnormal bleeding, prolonged cough, unexplained weight loss, change in bowel movementsCancer_cell_0_4_1
Risk factorsCancer_header_cell_0_5_0 Tobacco, obesity, poor diet, lack of physical activity, excessive alcohol, certain infectionsCancer_cell_0_5_1
TreatmentCancer_header_cell_0_6_0 Radiation therapy, surgery, chemotherapy, and targeted therapy.Cancer_cell_0_6_1
PrognosisCancer_header_cell_0_7_0 Average five year survival 66% (USA)Cancer_cell_0_7_1
FrequencyCancer_header_cell_0_8_0 90.5 million (2015)Cancer_cell_0_8_1
DeathsCancer_header_cell_0_9_0 8.8 million (2015)Cancer_cell_0_9_1

Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. Cancer_sentence_2

These contrast with benign tumors, which do not spread. Cancer_sentence_3

Possible signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained weight loss, and a change in bowel movements. Cancer_sentence_4

While these symptoms may indicate cancer, they can also have other causes. Cancer_sentence_5

Over 100 types of cancers affect humans. Cancer_sentence_6

Tobacco use is the cause of about 22% of cancer deaths. Cancer_sentence_7

Another 10% are due to obesity, poor diet, lack of physical activity or excessive drinking of alcohol. Cancer_sentence_8

Other factors include certain infections, exposure to ionizing radiation, and environmental pollutants. Cancer_sentence_9

In the developing world, 15% of cancers are due to infections such as Helicobacter pylori, hepatitis B, hepatitis C, human papillomavirus infection, Epstein–Barr virus and human immunodeficiency virus (HIV). Cancer_sentence_10

These factors act, at least partly, by changing the genes of a cell. Cancer_sentence_11

Typically, many genetic changes are required before cancer develops. Cancer_sentence_12

Approximately 5–10% of cancers are due to inherited genetic defects. Cancer_sentence_13

Cancer can be detected by certain signs and symptoms or screening tests. Cancer_sentence_14

It is then typically further investigated by medical imaging and confirmed by biopsy. Cancer_sentence_15

The risk of developing certain cancers can be reduced by not smoking, maintaining a healthy weight, limiting alcohol intake, eating plenty of vegetables, fruits, and whole grains, vaccination against certain infectious diseases, limiting consumption of processed meat and red meat, and limiting exposure to sunlight. Cancer_sentence_16

Early detection through screening is useful for cervical and colorectal cancer. Cancer_sentence_17

The benefits of screening in breast cancer are controversial. Cancer_sentence_18

Cancer is often treated with some combination of radiation therapy, surgery, chemotherapy and targeted therapy. Cancer_sentence_19

Pain and symptom management are an important part of care. Cancer_sentence_20

Palliative care is particularly important in people with advanced disease. Cancer_sentence_21

The chance of survival depends on the type of cancer and extent of disease at the start of treatment. Cancer_sentence_22

In children under 15 at diagnosis, the five-year survival rate in the developed world is on average 80%. Cancer_sentence_23

For cancer in the United States, the average five-year survival rate is 66%. Cancer_sentence_24

In 2015, about 90.5 million people had cancer. Cancer_sentence_25

As of 2019, about 18 million new cases occur annually. Cancer_sentence_26

Annually, it caused about 8.8 million deaths (15.7% of deaths). Cancer_sentence_27

The most common types of cancer in males are lung cancer, prostate cancer, colorectal cancer, and stomach cancer. Cancer_sentence_28

In females, the most common types are breast cancer, colorectal cancer, lung cancer, and cervical cancer. Cancer_sentence_29

If skin cancer other than melanoma were included in total new cancer cases each year, it would account for around 40% of cases. Cancer_sentence_30

In children, acute lymphoblastic leukemia and brain tumors are most common, except in Africa, where non-Hodgkin lymphoma occurs more often. Cancer_sentence_31

In 2012, about 165,000 children under 15 years of age were diagnosed with cancer. Cancer_sentence_32

The risk of cancer increases significantly with age, and many cancers occur more commonly in developed countries. Cancer_sentence_33

Rates are increasing as more people live to an old age and as lifestyle changes occur in the developing world. Cancer_sentence_34

The financial costs of cancer were estimated at 1.16 trillion USD per year as of 2010. Cancer_sentence_35

Etymology and definitions Cancer_section_0

The word comes from the ancient Greek καρκίνος, meaning crab and tumor. Cancer_sentence_36

Greek physicians Hippocrates and Galen, among others, noted similarity of crabs to some tumors with swollen veins. Cancer_sentence_37

The word was introduced in English in the modern medical sense c. 1600. Cancer_sentence_38

Cancers comprise a large family of diseases that involve abnormal cell growth with the potential to invade or spread to other parts of the body. Cancer_sentence_39

They form a subset of neoplasms. Cancer_sentence_40

A neoplasm or tumor is a group of cells that have undergone unregulated growth and will often form a mass or lump, but may be distributed diffusely. Cancer_sentence_41

All tumor cells show the six hallmarks of cancer. Cancer_sentence_42

These characteristics are required to produce a malignant tumor. Cancer_sentence_43

They include: Cancer_sentence_44

Cancer_unordered_list_0

The progression from normal cells to cells that can form a detectable mass to outright cancer involves multiple steps known as malignant progression. Cancer_sentence_45

Signs and symptoms Cancer_section_1

Main article: Cancer signs and symptoms Cancer_sentence_46

When cancer begins, it produces no symptoms. Cancer_sentence_47

Signs and symptoms appear as the mass grows or ulcerates. Cancer_sentence_48

The findings that result depend on the cancer's type and location. Cancer_sentence_49

Few symptoms are specific. Cancer_sentence_50

Many frequently occur in individuals who have other conditions. Cancer_sentence_51

Cancer can be difficult to diagnose and can be considered a "great imitator." Cancer_sentence_52

People may become anxious or depressed post-diagnosis. Cancer_sentence_53

The risk of suicide in people with cancer is approximately double. Cancer_sentence_54

Local symptoms Cancer_section_2

Local symptoms may occur due to the mass of the tumor or its ulceration. Cancer_sentence_55

For example, mass effects from lung cancer can block the bronchus resulting in cough or pneumonia; esophageal cancer can cause narrowing of the esophagus, making it difficult or painful to swallow; and colorectal cancer may lead to narrowing or blockages in the bowel, affecting bowel habits. Cancer_sentence_56

Masses in breasts or testicles may produce observable lumps. Cancer_sentence_57

Ulceration can cause bleeding that can lead to symptoms such as coughing up blood (lung cancer), anemia or rectal bleeding (colon cancer), blood in the urine (bladder cancer), or abnormal vaginal bleeding (endometrial or cervical cancer). Cancer_sentence_58

Although localized pain may occur in advanced cancer, the initial tumor is usually painless. Cancer_sentence_59

Some cancers can cause a buildup of fluid within the chest or . Cancer_sentence_60

Systemic symptoms Cancer_section_3

Systemic symptoms may occur due to the body's response to the cancer. Cancer_sentence_61

This may include fatigue, unintentional weight loss, or skin changes. Cancer_sentence_62

Some cancers can cause a systemic inflammatory state that leads to ongoing muscle loss and weakness, known as cachexia. Cancer_sentence_63

Some types of cancer such as Hodgkin disease, leukemias and cancers of the liver or kidney can cause a persistent fever. Cancer_sentence_64

Some systemic symptoms of cancer are caused by hormones or other molecules produced by the tumor, known as paraneoplastic syndromes. Cancer_sentence_65

Common paraneoplastic syndromes include hypercalcemia which can cause altered mental state, constipation and dehydration, or hyponatremia that can also cause altered mental status, vomiting, headache or seizures. Cancer_sentence_66

Metastasis Cancer_section_4

Main article: Metastasis Cancer_sentence_67

Metastasis is the spread of cancer to other locations in the body. Cancer_sentence_68

The dispersed tumors are called metastatic tumors, while the original is called the primary tumor. Cancer_sentence_69

Almost all cancers can metastasize. Cancer_sentence_70

Most cancer deaths are due to cancer that has metastasized. Cancer_sentence_71

Metastasis is common in the late stages of cancer and it can occur via the blood or the lymphatic system or both. Cancer_sentence_72

The typical steps in metastasis are local invasion, intravasation into the blood or lymph, circulation through the body, extravasation into the new tissue, proliferation and angiogenesis. Cancer_sentence_73

Different types of cancers tend to metastasize to particular organs, but overall the most common places for metastases to occur are the lungs, liver, brain and the bones. Cancer_sentence_74

Causes Cancer_section_5

Main article: Causes of cancer Cancer_sentence_75

The majority of cancers, some 90–95% of cases, are due to genetic mutations from environmental and lifestyle factors. Cancer_sentence_76

The remaining 5–10% are due to inherited genetics. Cancer_sentence_77

Environmental refers to any cause that is not inherited, such as lifestyle, economic, and behavioral factors and not merely pollution. Cancer_sentence_78

Common environmental factors that contribute to cancer death include tobacco use (25–30%), diet and obesity (30–35%), infections (15–20%), radiation (both ionizing and non-ionizing, up to 10%), lack of physical activity, and pollution. Cancer_sentence_79

Psychological stress does not appear to be a risk factor for the onset of cancer, though it may worsen outcomes in those who already have cancer. Cancer_sentence_80

It is not generally possible to prove what caused a particular cancer because the various causes do not have specific fingerprints. Cancer_sentence_81

For example, if a person who uses tobacco heavily develops lung cancer, then it was probably caused by the tobacco use, but since everyone has a small chance of developing lung cancer as a result of air pollution or radiation, the cancer may have developed for one of those reasons. Cancer_sentence_82

Excepting the rare transmissions that occur with pregnancies and occasional organ donors, cancer is generally not a transmissible disease. Cancer_sentence_83

Chemicals Cancer_section_6

Further information: Alcohol and cancer and Smoking and cancer Cancer_sentence_84

Exposure to particular substances have been linked to specific types of cancer. Cancer_sentence_85

These substances are called carcinogens. Cancer_sentence_86

Tobacco smoke, for example, causes 90% of lung cancer. Cancer_sentence_87

It also causes cancer in the larynx, head, neck, stomach, bladder, kidney, esophagus and pancreas. Cancer_sentence_88

Tobacco smoke contains over fifty known carcinogens, including nitrosamines and polycyclic aromatic hydrocarbons. Cancer_sentence_89

Tobacco is responsible for about one in five cancer deaths worldwide and about one in three in the developed world. Cancer_sentence_90

Lung cancer death rates in the United States have mirrored smoking patterns, with increases in smoking followed by dramatic increases in lung cancer death rates and, more recently, decreases in smoking rates since the 1950s followed by decreases in lung cancer death rates in men since 1990. Cancer_sentence_91

In Western Europe, 10% of cancers in males and 3% of cancers in females are attributed to alcohol exposure, especially liver and digestive tract cancers. Cancer_sentence_92

Cancer from work-related substance exposures may cause between 2 and 20% of cases, causing at least 200,000 deaths. Cancer_sentence_93

Cancers such as lung cancer and mesothelioma can come from inhaling tobacco smoke or asbestos fibers, or leukemia from exposure to benzene. Cancer_sentence_94

Diet and exercise Cancer_section_7

Main article: Diet and cancer Cancer_sentence_95

Diet, physical inactivity and obesity are related to up to 30–35% of cancer deaths. Cancer_sentence_96

In the United States, excess body weight is associated with the development of many types of cancer and is a factor in 14–20% of cancer deaths. Cancer_sentence_97

A UK study including data on over 5 million people showed higher body mass index to be related to at least 10 types of cancer and responsible for around 12,000 cases each year in that country. Cancer_sentence_98

Physical inactivity is believed to contribute to cancer risk, not only through its effect on body weight but also through negative effects on the immune system and endocrine system. Cancer_sentence_99

More than half of the effect from diet is due to overnutrition (eating too much), rather than from eating too few vegetables or other healthful foods. Cancer_sentence_100

Some specific foods are linked to specific cancers. Cancer_sentence_101

A high-salt diet is linked to gastric cancer. Cancer_sentence_102

Aflatoxin B1, a frequent food contaminant, causes liver cancer. Cancer_sentence_103

Betel nut chewing can cause oral cancer. Cancer_sentence_104

National differences in dietary practices may partly explain differences in cancer incidence. Cancer_sentence_105

For example, gastric cancer is more common in Japan due to its high-salt diet while colon cancer is more common in the United States. Cancer_sentence_106

Immigrant cancer profiles mirror those of their new country, often within one generation. Cancer_sentence_107

Infection Cancer_section_8

Main article: Infectious causes of cancer Cancer_sentence_108

Worldwide approximately 18% of cancer deaths are related to infectious diseases. Cancer_sentence_109

This proportion ranges from a high of 25% in Africa to less than 10% in the developed world. Cancer_sentence_110

Viruses are the usual infectious agents that cause cancer but cancer bacteria and parasites may also play a role. Cancer_sentence_111

Oncoviruses (viruses that can cause cancer) include human papillomavirus (cervical cancer), Epstein–Barr virus (B-cell lymphoproliferative disease and nasopharyngeal carcinoma), Kaposi's sarcoma herpesvirus (Kaposi's sarcoma and primary effusion lymphomas), hepatitis B and hepatitis C viruses (hepatocellular carcinoma) and human T-cell leukemia virus-1 (T-cell leukemias). Cancer_sentence_112

Bacterial infection may also increase the risk of cancer, as seen in Helicobacter pylori-induced gastric carcinoma. Cancer_sentence_113

Parasitic infections associated with cancer include Schistosoma haematobium (squamous cell carcinoma of the bladder) and the liver flukes, Opisthorchis viverrini and Clonorchis sinensis (cholangiocarcinoma). Cancer_sentence_114

Radiation Cancer_section_9

Main article: Radiation-induced cancer Cancer_sentence_115

Radiation exposure such as ultraviolet radiation and radioactive material is a risk factor for cancer. Cancer_sentence_116

Many non-melanoma skin cancers are due to ultraviolet radiation, mostly from sunlight. Cancer_sentence_117

Sources of ionizing radiation include medical imaging and radon gas. Cancer_sentence_118

Ionizing radiation is not a particularly strong mutagen. Cancer_sentence_119

Residential exposure to radon gas, for example, has similar cancer risks as passive smoking. Cancer_sentence_120

Radiation is a more potent source of cancer when combined with other cancer-causing agents, such as radon plus tobacco smoke. Cancer_sentence_121

Radiation can cause cancer in most parts of the body, in all animals and at any age. Cancer_sentence_122

Children are twice as likely to develop radiation-induced leukemia as adults; radiation exposure before birth has ten times the effect. Cancer_sentence_123

Medical use of ionizing radiation is a small but growing source of radiation-induced cancers. Cancer_sentence_124

Ionizing radiation may be used to treat other cancers, but this may, in some cases, induce a second form of cancer. Cancer_sentence_125

It is also used in some kinds of medical imaging. Cancer_sentence_126

Prolonged exposure to ultraviolet radiation from the sun can lead to melanoma and other skin malignancies. Cancer_sentence_127

Clear evidence establishes ultraviolet radiation, especially the non-ionizing medium wave UVB, as the cause of most non-melanoma skin cancers, which are the most common forms of cancer in the world. Cancer_sentence_128

Non-ionizing radio frequency radiation from mobile phones, electric power transmission and other similar sources has been described as a possible carcinogen by the World Health Organization's International Agency for Research on Cancer. Cancer_sentence_129

Evidence, however, has not supported a concern. Cancer_sentence_130

This includes that studies have not found a consistent link between mobile phone radiation and cancer risk. Cancer_sentence_131

Heredity Cancer_section_10

Main article: Cancer syndrome Cancer_sentence_132

The vast majority of cancers are non-hereditary (sporadic). Cancer_sentence_133

Hereditary cancers are primarily caused by an inherited genetic defect. Cancer_sentence_134

Less than 0.3% of the population are carriers of a genetic mutation that has a large effect on cancer risk and these cause less than 3–10% of cancer. Cancer_sentence_135

Some of these syndromes include: certain inherited mutations in the genes BRCA1 and BRCA2 with a more than 75% risk of breast cancer and ovarian cancer, and hereditary nonpolyposis colorectal cancer (HNPCC or Lynch syndrome), which is present in about 3% of people with colorectal cancer, among others. Cancer_sentence_136

Statistically for cancers causing most mortality, the relative risk of developing colorectal cancer when a first-degree relative (parent, sibling or child) has been diagnosed with it is about 2. Cancer_sentence_137

The corresponding relative risk is 1.5 for lung cancer, and 1.9 for prostate cancer. Cancer_sentence_138

For breast cancer, the relative risk is 1.8 with a first-degree relative having developed it at 50 years of age or older, and 3.3 when the relative developed it when being younger than 50 years of age. Cancer_sentence_139

Taller people have an increased risk of cancer because they have more cells than shorter people. Cancer_sentence_140

Since height is genetically determined to a large extent, taller people have a heritable increase of cancer risk. Cancer_sentence_141

Physical agents Cancer_section_11

Some substances cause cancer primarily through their physical, rather than chemical, effects. Cancer_sentence_142

A prominent example of this is prolonged exposure to asbestos, naturally occurring mineral fibers that are a major cause of mesothelioma (cancer of the serous membrane) usually the serous membrane surrounding the lungs. Cancer_sentence_143

Other substances in this category, including both naturally occurring and synthetic asbestos-like fibers, such as wollastonite, attapulgite, glass wool and rock wool, are believed to have similar effects. Cancer_sentence_144

Non-fibrous particulate materials that cause cancer include powdered metallic cobalt and nickel and crystalline silica (quartz, cristobalite and tridymite). Cancer_sentence_145

Usually, physical carcinogens must get inside the body (such as through inhalation) and require years of exposure to produce cancer. Cancer_sentence_146

Physical trauma resulting in cancer is relatively rare. Cancer_sentence_147

Claims that breaking bones resulted in bone cancer, for example, have not been proven. Cancer_sentence_148

Similarly, physical trauma is not accepted as a cause for cervical cancer, breast cancer or brain cancer. Cancer_sentence_149

One accepted source is frequent, long-term application of hot objects to the body. Cancer_sentence_150

It is possible that repeated burns on the same part of the body, such as those produced by kanger and kairo heaters (charcoal hand warmers), may produce skin cancer, especially if carcinogenic chemicals are also present. Cancer_sentence_151

Frequent consumption of scalding hot tea may produce esophageal cancer. Cancer_sentence_152

Generally, it is believed that cancer arises, or a pre-existing cancer is encouraged, during the process of healing, rather than directly by the trauma. Cancer_sentence_153

However, repeated injuries to the same tissues might promote excessive cell proliferation, which could then increase the odds of a cancerous mutation. Cancer_sentence_154

Chronic inflammation has been hypothesized to directly cause mutation. Cancer_sentence_155

Inflammation can contribute to proliferation, survival, angiogenesis and migration of cancer cells by influencing the tumor microenvironment. Cancer_sentence_156

Oncogenes build up an inflammatory pro-tumorigenic microenvironment. Cancer_sentence_157

Hormones Cancer_section_12

Some hormones play a role in the development of cancer by promoting cell proliferation. Cancer_sentence_158

Insulin-like growth factors and their binding proteins play a key role in cancer cell proliferation, differentiation and apoptosis, suggesting possible involvement in carcinogenesis. Cancer_sentence_159

Hormones are important agents in sex-related cancers, such as cancer of the breast, endometrium, prostate, ovary and testis and also of thyroid cancer and bone cancer. Cancer_sentence_160

For example, the daughters of women who have breast cancer have significantly higher levels of estrogen and progesterone than the daughters of women without breast cancer. Cancer_sentence_161

These higher hormone levels may explain their higher risk of breast cancer, even in the absence of a breast-cancer gene. Cancer_sentence_162

Similarly, men of African ancestry have significantly higher levels of testosterone than men of European ancestry and have a correspondingly higher level of prostate cancer. Cancer_sentence_163

Men of Asian ancestry, with the lowest levels of testosterone-activating androstanediol glucuronide, have the lowest levels of prostate cancer. Cancer_sentence_164

Other factors are relevant: obese people have higher levels of some hormones associated with cancer and a higher rate of those cancers. Cancer_sentence_165

Women who take hormone replacement therapy have a higher risk of developing cancers associated with those hormones. Cancer_sentence_166

On the other hand, people who exercise far more than average have lower levels of these hormones and lower risk of cancer. Cancer_sentence_167

Osteosarcoma may be promoted by growth hormones. Cancer_sentence_168

Some treatments and prevention approaches leverage this cause by artificially reducing hormone levels and thus discouraging hormone-sensitive cancers. Cancer_sentence_169

Autoimmune diseases Cancer_section_13

There is an association between celiac disease and an increased risk of all cancers. Cancer_sentence_170

People with untreated celiac disease have a higher risk, but this risk decreases with time after diagnosis and strict treatment, probably due to the adoption of a gluten-free diet, which seems to have a protective role against development of malignancy in people with celiac disease. Cancer_sentence_171

However, the delay in diagnosis and initiation of a gluten-free diet seems to increase the risk of malignancies. Cancer_sentence_172

Rates of gastrointestinal cancers are increased in people with Crohn's disease and ulcerative colitis, due to chronic inflammation. Cancer_sentence_173

Also, immunomodulators and biologic agents used to treat these diseases may promote developing extra-intestinal malignancies. Cancer_sentence_174

Pathophysiology Cancer_section_14

Main article: Carcinogenesis Cancer_sentence_175

Genetics Cancer_section_15

Main article: Oncogenomics Cancer_sentence_176

Cancer is fundamentally a disease of tissue growth regulation. Cancer_sentence_177

In order for a normal cell to transform into a cancer cell, the genes that regulate cell growth and differentiation must be altered. Cancer_sentence_178

The affected genes are divided into two broad categories. Cancer_sentence_179

Oncogenes are genes that promote cell growth and reproduction. Cancer_sentence_180

Tumor suppressor genes are genes that inhibit cell division and survival. Cancer_sentence_181

Malignant transformation can occur through the formation of novel oncogenes, the inappropriate over-expression of normal oncogenes, or by the under-expression or disabling of tumor suppressor genes. Cancer_sentence_182

Typically, changes in multiple genes are required to transform a normal cell into a cancer cell. Cancer_sentence_183

Genetic changes can occur at different levels and by different mechanisms. Cancer_sentence_184

The gain or loss of an entire chromosome can occur through errors in mitosis. Cancer_sentence_185

More common are mutations, which are changes in the nucleotide sequence of genomic DNA. Cancer_sentence_186

Large-scale mutations involve the deletion or gain of a portion of a chromosome. Cancer_sentence_187

Genomic amplification occurs when a cell gains copies (often 20 or more) of a small chromosomal locus, usually containing one or more oncogenes and adjacent genetic material. Cancer_sentence_188

Translocation occurs when two separate chromosomal regions become abnormally fused, often at a characteristic location. Cancer_sentence_189

A well-known example of this is the Philadelphia chromosome, or translocation of chromosomes 9 and 22, which occurs in chronic myelogenous leukemia and results in production of the BCR-abl fusion protein, an oncogenic tyrosine kinase. Cancer_sentence_190

Small-scale mutations include point mutations, deletions, and insertions, which may occur in the promoter region of a gene and affect its expression, or may occur in the gene's coding sequence and alter the function or stability of its protein product. Cancer_sentence_191

Disruption of a single gene may also result from integration of genomic material from a DNA virus or retrovirus, leading to the expression of viral oncogenes in the affected cell and its descendants. Cancer_sentence_192

Replication of the data contained within the DNA of living cells will probabilistically result in some errors (mutations). Cancer_sentence_193

Complex error correction and prevention is built into the process and safeguards the cell against cancer. Cancer_sentence_194

If a significant error occurs, the damaged cell can self-destruct through programmed cell death, termed apoptosis. Cancer_sentence_195

If the error control processes fail, then the mutations will survive and be passed along to daughter cells. Cancer_sentence_196

Some environments make errors more likely to arise and propagate. Cancer_sentence_197

Such environments can include the presence of disruptive substances called carcinogens, repeated physical injury, heat, ionising radiation or hypoxia. Cancer_sentence_198

The errors that cause cancer are self-amplifying and compounding, for example: Cancer_sentence_199

Cancer_unordered_list_1

  • A mutation in the error-correcting machinery of a cell might cause that cell and its children to accumulate errors more rapidly.Cancer_item_1_6
  • A further mutation in an oncogene might cause the cell to reproduce more rapidly and more frequently than its normal counterparts.Cancer_item_1_7
  • A further mutation may cause loss of a tumor suppressor gene, disrupting the apoptosis signaling pathway and immortalizing the cell.Cancer_item_1_8
  • A further mutation in the signaling machinery of the cell might send error-causing signals to nearby cells.Cancer_item_1_9

The transformation of a normal cell into cancer is akin to a chain reaction caused by initial errors, which compound into more severe errors, each progressively allowing the cell to escape more controls that limit normal tissue growth. Cancer_sentence_200

This rebellion-like scenario is an undesirable survival of the fittest, where the driving forces of evolution work against the body's design and enforcement of order. Cancer_sentence_201

Once cancer has begun to develop, this ongoing process, termed clonal evolution, drives progression towards more invasive stages. Cancer_sentence_202

Clonal evolution leads to intra-tumour heterogeneity (cancer cells with heterogeneous mutations) that complicates designing effective treatment strategies. Cancer_sentence_203

Characteristic abilities developed by cancers are divided into categories, specifically evasion of apoptosis, self-sufficiency in growth signals, insensitivity to anti-growth signals, sustained angiogenesis, limitless replicative potential, metastasis, reprogramming of energy metabolism and evasion of immune destruction. Cancer_sentence_204

Epigenetics Cancer_section_16

Main article: Cancer epigenetics Cancer_sentence_205

The classical view of cancer is a set of diseases that are driven by progressive genetic abnormalities that include mutations in tumor-suppressor genes and oncogenes and chromosomal abnormalities. Cancer_sentence_206

Later epigenetic alterations' role was identified. Cancer_sentence_207

Epigenetic alterations are functionally relevant modifications to the genome that do not change the nucleotide sequence. Cancer_sentence_208

Examples of such modifications are changes in DNA methylation (hypermethylation and hypomethylation), histone modification and changes in chromosomal architecture (caused by inappropriate expression of proteins such as HMGA2 or HMGA1). Cancer_sentence_209

Each of these alterations regulates gene expression without altering the underlying DNA sequence. Cancer_sentence_210

These changes may remain through cell divisions, last for multiple generations and can be considered to be epimutations (equivalent to mutations). Cancer_sentence_211

Epigenetic alterations occur frequently in cancers. Cancer_sentence_212

As an example, one study listed protein coding genes that were frequently altered in their methylation in association with colon cancer. Cancer_sentence_213

These included 147 hypermethylated and 27 hypomethylated genes. Cancer_sentence_214

Of the hypermethylated genes, 10 were hypermethylated in 100% of colon cancers and many others were hypermethylated in more than 50% of colon cancers. Cancer_sentence_215

While epigenetic alterations are found in cancers, the epigenetic alterations in DNA repair genes, causing reduced expression of DNA repair proteins, may be of particular importance. Cancer_sentence_216

Such alterations are thought to occur early in progression to cancer and to be a likely cause of the genetic instability characteristic of cancers. Cancer_sentence_217

Reduced expression of DNA repair genes disrupts DNA repair. Cancer_sentence_218

This is shown in the figure at the 4th level from the top. Cancer_sentence_219

(In the figure, red wording indicates the central role of DNA damage and defects in DNA repair in progression to cancer.) Cancer_sentence_220

When DNA repair is deficient DNA damage remains in cells at a higher than usual level (5th level) and cause increased frequencies of mutation and/or epimutation (6th level). Cancer_sentence_221

Mutation rates increase substantially in cells defective in DNA mismatch repair or in homologous recombinational repair (HRR). Cancer_sentence_222

Chromosomal rearrangements and aneuploidy also increase in HRR defective cells. Cancer_sentence_223

Higher levels of DNA damage cause increased mutation (right side of figure) and increased epimutation. Cancer_sentence_224

During repair of DNA double strand breaks, or repair of other DNA damage, incompletely cleared repair sites can cause epigenetic gene silencing. Cancer_sentence_225

Deficient expression of DNA repair proteins due to an inherited mutation can increase cancer risks. Cancer_sentence_226

Individuals with an inherited impairment in any of 34 DNA repair genes (see article DNA repair-deficiency disorder) have increased cancer risk, with some defects ensuring a 100% lifetime chance of cancer (e.g. p53 mutations). Cancer_sentence_227

Germ line DNA repair mutations are noted on the figure's left side. Cancer_sentence_228

However, such germline mutations (which cause highly penetrant cancer syndromes) are the cause of only about 1 percent of cancers. Cancer_sentence_229

In sporadic cancers, deficiencies in DNA repair are occasionally caused by a mutation in a DNA repair gene but are much more frequently caused by epigenetic alterations that reduce or silence expression of DNA repair genes. Cancer_sentence_230

This is indicated in the figure at the 3rd level. Cancer_sentence_231

Many studies of heavy metal-induced carcinogenesis show that such heavy metals cause a reduction in expression of DNA repair enzymes, some through epigenetic mechanisms. Cancer_sentence_232

DNA repair inhibition is proposed to be a predominant mechanism in heavy metal-induced carcinogenicity. Cancer_sentence_233

In addition, frequent epigenetic alterations of the DNA sequences code for small RNAs called microRNAs (or miRNAs). Cancer_sentence_234

miRNAs do not code for proteins, but can "target" protein-coding genes and reduce their expression. Cancer_sentence_235

Cancers usually arise from an assemblage of mutations and epimutations that confer a selective advantage leading to clonal expansion (see Field defects in progression to cancer). Cancer_sentence_236

Mutations, however, may not be as frequent in cancers as epigenetic alterations. Cancer_sentence_237

An average cancer of the breast or colon can have about 60 to 70 protein-altering mutations, of which about three or four may be "driver" mutations and the remaining ones may be "passenger" mutations. Cancer_sentence_238

Metastasis Cancer_section_17

Main article: Metastasis Cancer_sentence_239

Metastasis is the spread of cancer to other locations in the body. Cancer_sentence_240

The dispersed tumors are called metastatic tumors, while the original is called the primary tumor. Cancer_sentence_241

Almost all cancers can metastasize. Cancer_sentence_242

Most cancer deaths are due to cancer that has metastasized. Cancer_sentence_243

Metastasis is common in the late stages of cancer and it can occur via the blood or the lymphatic system or both. Cancer_sentence_244

The typical steps in metastasis are local invasion, intravasation into the blood or lymph, circulation through the body, extravasation into the new tissue, proliferation and angiogenesis. Cancer_sentence_245

Different types of cancers tend to metastasize to particular organs, but overall the most common places for metastases to occur are the lungs, liver, brain and the bones. Cancer_sentence_246

Metabolism Cancer_section_18

Main article: Tumor metabolome Cancer_sentence_247

Normal cells typically generate only about 30% of energy from glycolysis, whereas most cancers rely on glycolysis for energy production (Warburg effect). Cancer_sentence_248

But a minority of cancer types rely on oxidative phosphorylation as the primary energy source, including lymphoma, leukemia, and endometrial cancer. Cancer_sentence_249

Even in these cases, however, the use of glycolysis as an energy source rarely exceeds 60%. Cancer_sentence_250

A few cancers use glutamine as the major energy source, partly because it provides nitrogen required for nucleotide (DNA,RNA) synthesis. Cancer_sentence_251

Cancer stem cells often use oxidative phosphorylation or glutamine as a primary energy source. Cancer_sentence_252

Several studies have indicated that the enzyme sirtuin 6 is selectively inactivated during oncogenesis in a variety of tumor types by inducing glycolysis. Cancer_sentence_253

Another sirtuin, sirtuin 3 inhibits cancers that depend upon glycolysis, but promotes cancers that depend upon oxidative phosphorylation. Cancer_sentence_254

A low-carbohydrate diet (ketogenic diet) has been sometimes been recommended as a supportive therapy for cancer treatment. Cancer_sentence_255

Diagnosis Cancer_section_19

Most cancers are initially recognized either because of the appearance of signs or symptoms or through screening. Cancer_sentence_256

Neither of these leads to a definitive diagnosis, which requires the examination of a tissue sample by a pathologist. Cancer_sentence_257

People with suspected cancer are investigated with medical tests. Cancer_sentence_258

These commonly include blood tests, X-rays, (contrast) CT scans and endoscopy. Cancer_sentence_259

The tissue diagnosis from the biopsy indicates the type of cell that is proliferating, its histological grade, genetic abnormalities and other features. Cancer_sentence_260

Together, this information is useful to evaluate the prognosis and to choose the best treatment. Cancer_sentence_261

Cytogenetics and immunohistochemistry are other types of tissue tests. Cancer_sentence_262

These tests provide information about molecular changes (such as mutations, fusion genes and numerical chromosome changes) and may thus also indicate the prognosis and best treatment. Cancer_sentence_263

Cancer diagnosis can cause psychological distress and psychosocial interventions, such as talking therapy, may help people with this. Cancer_sentence_264

Classification Cancer_section_20

Further information: List of cancer types and List of oncology-related terms Cancer_sentence_265

Cancers are classified by the type of cell that the tumor cells resemble and is therefore presumed to be the origin of the tumor. Cancer_sentence_266

These types include: Cancer_sentence_267

Cancer_unordered_list_2

Cancers are usually named using -carcinoma, -sarcoma or -blastoma as a suffix, with the Latin or Greek word for the organ or tissue of origin as the root. Cancer_sentence_268

For example, cancers of the liver parenchyma arising from malignant epithelial cells is called hepatocarcinoma, while a malignancy arising from primitive liver precursor cells is called a hepatoblastoma and a cancer arising from fat cells is called a liposarcoma. Cancer_sentence_269

For some common cancers, the English organ name is used. Cancer_sentence_270

For example, the most common type of breast cancer is called ductal carcinoma of the breast. Cancer_sentence_271

Here, the adjective ductal refers to the appearance of cancer under the microscope, which suggests that it has originated in the milk ducts. Cancer_sentence_272

Benign tumors (which are not cancers) are named using -oma as a suffix with the organ name as the root. Cancer_sentence_273

For example, a benign tumor of smooth muscle cells is called a leiomyoma (the common name of this frequently occurring benign tumor in the uterus is fibroid). Cancer_sentence_274

Confusingly, some types of cancer use the -noma suffix, examples including melanoma and seminoma. Cancer_sentence_275

Some types of cancer are named for the size and shape of the cells under a microscope, such as giant cell carcinoma, spindle cell carcinoma and small-cell carcinoma. Cancer_sentence_276

Cancer_unordered_list_3

  • Cancer_item_3_15
  • Cancer_item_3_16
  • Cancer_item_3_17
  • Cancer_item_3_18

Prevention Cancer_section_21

Main article: Cancer prevention Cancer_sentence_277

Cancer prevention is defined as active measures to decrease cancer risk. Cancer_sentence_278

The vast majority of cancer cases are due to environmental risk factors. Cancer_sentence_279

Many of these environmental factors are controllable lifestyle choices. Cancer_sentence_280

Thus, cancer is generally preventable. Cancer_sentence_281

Between 70% and 90% of common cancers are due to environmental factors and therefore potentially preventable. Cancer_sentence_282

Greater than 30% of cancer deaths could be prevented by avoiding risk factors including: tobacco, excess weight/obesity, poor diet, physical inactivity, alcohol, sexually transmitted infections and air pollution. Cancer_sentence_283

Not all environmental causes are controllable, such as naturally occurring background radiation and cancers caused through hereditary genetic disorders and thus are not preventable via personal behavior. Cancer_sentence_284

Dietary Cancer_section_22

Main article: Diet and cancer Cancer_sentence_285

While many dietary recommendations have been proposed to reduce cancer risks, the evidence to support them is not definitive. Cancer_sentence_286

The primary dietary factors that increase risk are obesity and alcohol consumption. Cancer_sentence_287

Diets low in fruits and vegetables and high in red meat have been implicated but reviews and meta-analyses do not come to a consistent conclusion. Cancer_sentence_288

A 2014 meta-analysis found no relationship between fruits and vegetables and cancer. Cancer_sentence_289

Coffee is associated with a reduced risk of liver cancer. Cancer_sentence_290

Studies have linked excess consumption of red or processed meat to an increased risk of breast cancer, colon cancer and pancreatic cancer, a phenomenon that could be due to the presence of carcinogens in meats cooked at high temperatures. Cancer_sentence_291

In 2015 the IARC reported that eating processed meat (e.g., bacon, ham, hot dogs, sausages) and, to a lesser degree, red meat was linked to some cancers. Cancer_sentence_292

Dietary recommendations for cancer prevention typically include an emphasis on vegetables, fruit, whole grains and fish and an avoidance of processed and red meat (beef, pork, lamb), animal fats, pickled foods and refined carbohydrates. Cancer_sentence_293

Medication Cancer_section_23

Medications can be used to prevent cancer in a few circumstances. Cancer_sentence_294

In the general population, NSAIDs reduce the risk of colorectal cancer; however, due to cardiovascular and gastrointestinal side effects, they cause overall harm when used for prevention. Cancer_sentence_295

Aspirin has been found to reduce the risk of death from cancer by about 7%. Cancer_sentence_296

COX-2 inhibitors may decrease the rate of polyp formation in people with familial adenomatous polyposis; however, it is associated with the same adverse effects as NSAIDs. Cancer_sentence_297

Daily use of tamoxifen or raloxifene reduce the risk of breast cancer in high-risk women. Cancer_sentence_298

The benefit versus harm for 5-alpha-reductase inhibitor such as finasteride is not clear. Cancer_sentence_299

Vitamin supplementation does not appear to be effective at preventing cancer. Cancer_sentence_300

While low blood levels of vitamin D are correlated with increased cancer risk, whether this relationship is causal and vitamin D supplementation is protective is not determined. Cancer_sentence_301

One 2014 review found that supplements had no significant effect on cancer risk. Cancer_sentence_302

Another 2014 review concluded that vitamin D3 may decrease the risk of death from cancer (one fewer death in 150 people treated over 5 years), but concerns with the quality of the data were noted. Cancer_sentence_303

Beta-Carotene supplementation increases lung cancer rates in those who are high risk. Cancer_sentence_304

Folic acid supplementation is not effective in preventing colon cancer and may increase colon polyps. Cancer_sentence_305

Selenium supplementation has not been shown to reduce the risk of cancer. Cancer_sentence_306

Vaccination Cancer_section_24

Vaccines have been developed that prevent infection by some carcinogenic viruses. Cancer_sentence_307

Human papillomavirus vaccine (Gardasil and Cervarix) decrease the risk of developing cervical cancer. Cancer_sentence_308

The hepatitis B vaccine prevents infection with hepatitis B virus and thus decreases the risk of liver cancer. Cancer_sentence_309

The administration of human papillomavirus and hepatitis B vaccinations is recommended where resources allow. Cancer_sentence_310

Screening Cancer_section_25

Main article: Cancer screening Cancer_sentence_311

Unlike diagnostic efforts prompted by symptoms and medical signs, cancer screening involves efforts to detect cancer after it has formed, but before any noticeable symptoms appear. Cancer_sentence_312

This may involve physical examination, blood or urine tests or medical imaging. Cancer_sentence_313

Cancer screening is not available for many types of cancers. Cancer_sentence_314

Even when tests are available, they may not be recommended for everyone. Cancer_sentence_315

Universal screening or mass screening involves screening everyone. Cancer_sentence_316

Selective screening identifies people who are at higher risk, such as people with a family history. Cancer_sentence_317

Several factors are considered to determine whether the benefits of screening outweigh the risks and the costs of screening. Cancer_sentence_318

These factors include: Cancer_sentence_319

Cancer_unordered_list_4

  • Possible harms from the screening test: for example, X-ray images involve exposure to potentially harmful ionizing radiationCancer_item_4_19
  • The likelihood of the test correctly identifying cancerCancer_item_4_20
  • The likelihood that cancer is present: Screening is not normally useful for rare cancers.Cancer_item_4_21
  • Possible harms from follow-up proceduresCancer_item_4_22
  • Whether suitable treatment is availableCancer_item_4_23
  • Whether early detection improves treatment outcomesCancer_item_4_24
  • Whether the cancer will ever need treatmentCancer_item_4_25
  • Whether the test is acceptable to the people: If a screening test is too burdensome (for example, extremely painful), then people will refuse to participate.Cancer_item_4_26
  • CostCancer_item_4_27

Recommendations Cancer_section_26

U.S. Preventive Services Task Force Cancer_section_27

The U.S. Cancer_sentence_320 Preventive Services Task Force (USPSTF) issues recommendations for various cancers: Cancer_sentence_321

Cancer_unordered_list_5

Japan Cancer_section_28

Screens for gastric cancer using photofluorography due to the high incidence there. Cancer_sentence_322

Genetic testing Cancer_section_29

See also: Cancer syndrome Cancer_sentence_323

Cancer_table_general_1

GeneCancer_header_cell_1_0_0 Cancer typesCancer_header_cell_1_0_1
BRCA1, BRCA2Cancer_cell_1_1_0 Breast, ovarian, pancreaticCancer_cell_1_1_1
HNPCC, MLH1, MSH2, MSH6, PMS1, PMS2Cancer_cell_1_2_0 Colon, uterine, small bowel, stomach, urinary tractCancer_cell_1_2_1

Genetic testing for individuals at high-risk of certain cancers is recommended by unofficial groups. Cancer_sentence_324

Carriers of these mutations may then undergo enhanced surveillance, chemoprevention, or preventative surgery to reduce their subsequent risk. Cancer_sentence_325

Management Cancer_section_30

Main articles: Management of cancer and oncology Cancer_sentence_326

Many treatment options for cancer exist. Cancer_sentence_327

The primary ones include surgery, chemotherapy, radiation therapy, hormonal therapy, targeted therapy and palliative care. Cancer_sentence_328

Which treatments are used depends on the type, location and grade of the cancer as well as the patient's health and preferences. Cancer_sentence_329

The treatment intent may or may not be curative. Cancer_sentence_330

Chemotherapy Cancer_section_31

Chemotherapy is the treatment of cancer with one or more cytotoxic anti-neoplastic drugs (chemotherapeutic agents) as part of a standardized regimen. Cancer_sentence_331

The term encompasses a variety of drugs, which are divided into broad categories such as alkylating agents and antimetabolites. Cancer_sentence_332

Traditional chemotherapeutic agents act by killing cells that divide rapidly, a critical property of most cancer cells. Cancer_sentence_333

It was found that providing combined cytotoxic drugs is better than a single drug; a process called the combination therapy; which has an advantage in the statistics of survival and response to the tumor and in the progress of the disease. Cancer_sentence_334

A Cochrane review concluded that combined therapy was more effective to treat metastasized breast cancer. Cancer_sentence_335

However, generally it is not certain whether combination chemotherapy leads to better health outcomes, when both survival and toxicity are considered. Cancer_sentence_336

Targeted therapy is a form of chemotherapy that targets specific molecular differences between cancer and normal cells. Cancer_sentence_337

The first targeted therapies blocked the estrogen receptor molecule, inhibiting the growth of breast cancer. Cancer_sentence_338

Another common example is the class of Bcr-Abl inhibitors, which are used to treat chronic myelogenous leukemia (CML). Cancer_sentence_339

Currently, targeted therapies exist for many of the most common cancer types, including bladder cancer, breast cancer, colorectal cancer, kidney cancer, leukemia, liver cancer, lung cancer, lymphoma, pancreatic cancer, prostate cancer, skin cancer, and thyroid cancer as well as other cancer types. Cancer_sentence_340

The efficacy of chemotherapy depends on the type of cancer and the stage. Cancer_sentence_341

In combination with surgery, chemotherapy has proven useful in cancer types including breast cancer, colorectal cancer, pancreatic cancer, osteogenic sarcoma, testicular cancer, ovarian cancer and certain lung cancers. Cancer_sentence_342

Chemotherapy is curative for some cancers, such as some leukemias, ineffective in some brain tumors, and needless in others, such as most non-melanoma skin cancers. Cancer_sentence_343

The effectiveness of chemotherapy is often limited by its toxicity to other tissues in the body. Cancer_sentence_344

Even when chemotherapy does not provide a permanent cure, it may be useful to reduce symptoms such as pain or to reduce the size of an inoperable tumor in the hope that surgery will become possible in the future. Cancer_sentence_345

Radiation Cancer_section_32

Radiation therapy involves the use of ionizing radiation in an attempt to either cure or improve symptoms. Cancer_sentence_346

It works by damaging the DNA of cancerous tissue, killing it. Cancer_sentence_347

To spare normal tissues (such as skin or organs, which radiation must pass through to treat the tumor), shaped radiation beams are aimed from multiple exposure angles to intersect at the tumor, providing a much larger dose there than in the surrounding, healthy tissue. Cancer_sentence_348

As with chemotherapy, cancers vary in their response to radiation therapy. Cancer_sentence_349

Radiation therapy is used in about half of cases. Cancer_sentence_350

The radiation can be either from internal sources (brachytherapy) or external sources. Cancer_sentence_351

The radiation is most commonly low energy X-rays for treating skin cancers, while higher energy X-rays are used for cancers within the body. Cancer_sentence_352

Radiation is typically used in addition to surgery and or chemotherapy. Cancer_sentence_353

For certain types of cancer, such as early head and neck cancer, it may be used alone. Cancer_sentence_354

For painful bone metastasis, it has been found to be effective in about 70% of patients. Cancer_sentence_355

Surgery Cancer_section_33

Surgery is the primary method of treatment for most isolated, solid cancers and may play a role in palliation and prolongation of survival. Cancer_sentence_356

It is typically an important part of definitive diagnosis and staging of tumors, as biopsies are usually required. Cancer_sentence_357

In localized cancer, surgery typically attempts to remove the entire mass along with, in certain cases, the lymph nodes in the area. Cancer_sentence_358

For some types of cancer this is sufficient to eliminate the cancer. Cancer_sentence_359

Palliative care Cancer_section_34

Palliative care is treatment that attempts to help the patient feel better and may be combined with an attempt to treat the cancer. Cancer_sentence_360

Palliative care includes action to reduce physical, emotional, spiritual and psycho-social distress. Cancer_sentence_361

Unlike treatment that is aimed at directly killing cancer cells, the primary goal of palliative care is to improve quality of life. Cancer_sentence_362

People at all stages of cancer treatment typically receive some kind of palliative care. Cancer_sentence_363

In some cases, medical specialty professional organizations recommend that patients and physicians respond to cancer only with palliative care. Cancer_sentence_364

This applies to patients who: Cancer_sentence_365

Cancer_ordered_list_6

  1. display low performance status, implying limited ability to care for themselvesCancer_item_6_33
  2. received no benefit from prior evidence-based treatmentsCancer_item_6_34
  3. are not eligible to participate in any appropriate clinical trialCancer_item_6_35
  4. no strong evidence implies that treatment would be effectiveCancer_item_6_36

Palliative care may be confused with hospice and therefore only indicated when people approach end of life. Cancer_sentence_366

Like hospice care, palliative care attempts to help the patient cope with their immediate needs and to increase comfort. Cancer_sentence_367

Unlike hospice care, palliative care does not require people to stop treatment aimed at the cancer. Cancer_sentence_368

Multiple national medical guidelines recommend early palliative care for patients whose cancer has produced distressing symptoms or who need help coping with their illness. Cancer_sentence_369

In patients first diagnosed with metastatic disease, palliative care may be immediately indicated. Cancer_sentence_370

Palliative care is indicated for patients with a prognosis of less than 12 months of life even given aggressive treatment. Cancer_sentence_371

Immunotherapy Cancer_section_35

Main article: Cancer immunotherapy Cancer_sentence_372

A variety of therapies using immunotherapy, stimulating or helping the immune system to fight cancer, have come into use since 1997. Cancer_sentence_373

Approaches include antibodies, checkpoint therapy, and adoptive cell transfer. Cancer_sentence_374

Laser therapy Cancer_section_36

Main article: Lasers in cancer treatment Cancer_sentence_375

Laser therapy uses high-intensity light to treat cancer by shrinking or destroying tumors or precancerous growths. Cancer_sentence_376

Lasers are most commonly used to treat superficial cancers that are on the surface of the body or the lining of internal organs. Cancer_sentence_377

It is used to treat basal cell skin cancer and the very early stages of others like cervical, penile, vaginal, vulvar, and non-small cell lung cancer. Cancer_sentence_378

It is often combined with other treatments, such as surgery, chemotherapy, or radiation therapy. Cancer_sentence_379

Laser-induced interstitial thermotherapy (LITT), or interstitial laser photocoagulation, uses lasers to treat some cancers using hyperthermia, which uses heat to shrink tumors by damaging or killing cancer cells. Cancer_sentence_380

Laser are more precise than surgery and cause less damage, pain, bleeding, swelling, and scarring. Cancer_sentence_381

A disadvantage is surgeons must have specialized training. Cancer_sentence_382

It may be more expensive than other treatments. Cancer_sentence_383

Alternative medicine Cancer_section_37

Complementary and alternative cancer treatments are a diverse group of therapies, practices and products that are not part of conventional medicine. Cancer_sentence_384

"Complementary medicine" refers to methods and substances used along with conventional medicine, while "alternative medicine" refers to compounds used instead of conventional medicine. Cancer_sentence_385

Most complementary and alternative medicines for cancer have not been studied or tested using conventional techniques such as clinical trials. Cancer_sentence_386

Some alternative treatments have been investigated and shown to be ineffective but still continue to be marketed and promoted. Cancer_sentence_387

Cancer researcher Andrew J. Vickers stated, "The label 'unproven' is inappropriate for such therapies; it is time to assert that many alternative cancer therapies have been 'disproven'." Cancer_sentence_388

Prognosis Cancer_section_38

See also: Cancer survival rates, List of cancer mortality rates in the United States, and Cancer survivor Cancer_sentence_389

Survival rates vary by cancer type and by the stage at which it is diagnosed, ranging from majority survival to complete mortality five years after diagnosis. Cancer_sentence_390

Once a cancer has metastasized, prognosis normally becomes much worse. Cancer_sentence_391

About half of patients receiving treatment for invasive cancer (excluding carcinoma in situ and non-melanoma skin cancers) die from that cancer or its treatment. Cancer_sentence_392

A majority of cancer deaths are due to metastases of the primary tumor. Cancer_sentence_393

Survival is worse in the developing world, partly because the types of cancer that are most common there are harder to treat than those associated with developed countries. Cancer_sentence_394

Those who survive cancer develop a second primary cancer at about twice the rate of those never diagnosed. Cancer_sentence_395

The increased risk is believed to be due to the random chance of developing any cancer, the likelihood of surviving the first cancer, the same risk factors that produced the first cancer, unwanted side effects of treating the first cancer (particularly radiation therapy), and to better compliance with screening. Cancer_sentence_396

Predicting short- or long-term survival depends on many factors. Cancer_sentence_397

The most important are the cancer type and the patient's age and overall health. Cancer_sentence_398

Those who are with other health problems have lower survival rates than otherwise healthy people. Cancer_sentence_399

Centenarians are unlikely to survive for five years even if treatment is successful. Cancer_sentence_400

People who report a higher quality of life tend to survive longer. Cancer_sentence_401

People with lower quality of life may be affected by depression and other complications and/or disease progression that both impairs quality and quantity of life. Cancer_sentence_402

Additionally, patients with worse prognoses may be depressed or report poorer quality of life because they perceive that their condition is likely to be fatal. Cancer_sentence_403

People with cancer have an increased risk of blood clots in their veins which can be life-threatening. Cancer_sentence_404

The use of blood thinners such as heparin decrease the risk of blood clots but have not been shown to increase survival in people with cancer. Cancer_sentence_405

People who take blood thinners also have an increased risk of bleeding. Cancer_sentence_406

Epidemiology Cancer_section_39

Main article: Epidemiology of cancer Cancer_sentence_407

See also: List of countries by cancer rate Cancer_sentence_408

Estimates are that in 2018, 18.1 million new cases of cancer and 9.6 million deaths occur globally. Cancer_sentence_409

About 20% of males and 17% of females will get cancer at some point in time while 13% of males and 9% of females will die from it. Cancer_sentence_410

In 2008, approximately 12.7 million cancers were diagnosed (excluding non-melanoma skin cancers and other non-invasive cancers) and in 2010 nearly 7.98 million people died. Cancer_sentence_411

Cancers account for approximately 16% of deaths. Cancer_sentence_412

The most common as of 2018 are lung cancer (1.76 million deaths), colorectal cancer (860,000) stomach cancer (780,000), liver cancer (780,000), and breast cancer (620,000). Cancer_sentence_413

This makes invasive cancer the leading cause of death in the developed world and the second leading in the developing world. Cancer_sentence_414

Over half of cases occur in the developing world. Cancer_sentence_415

Deaths from cancer were 5.8 million in 1990. Cancer_sentence_416

Deaths have been increasing primarily due to longer lifespans and lifestyle changes in the developing world. Cancer_sentence_417

The most significant risk factor for developing cancer is age. Cancer_sentence_418

Although it is possible for cancer to strike at any age, most patients with invasive cancer are over 65. Cancer_sentence_419

According to cancer researcher Robert A. Weinberg, "If we lived long enough, sooner or later we all would get cancer." Cancer_sentence_420

Some of the association between aging and cancer is attributed to immunosenescence, errors accumulated in DNA over a lifetime and age-related changes in the endocrine system. Cancer_sentence_421

Aging's effect on cancer is complicated by factors such as DNA damage and inflammation promoting it and factors such as vascular aging and endocrine changes inhibiting it. Cancer_sentence_422

Some slow-growing cancers are particularly common, but often are not fatal. Cancer_sentence_423

Autopsy studies in Europe and Asia showed that up to 36% of people have undiagnosed and apparently harmless thyroid cancer at the time of their deaths and that 80% of men develop prostate cancer by age 80. Cancer_sentence_424

As these cancers do not cause the patient's death, identifying them would have represented overdiagnosis rather than useful medical care. Cancer_sentence_425

The three most common childhood cancers are leukemia (34%), brain tumors (23%) and lymphomas (12%). Cancer_sentence_426

In the United States cancer affects about 1 in 285 children. Cancer_sentence_427

Rates of childhood cancer increased by 0.6% per year between 1975 and 2002 in the United States and by 1.1% per year between 1978 and 1997 in Europe. Cancer_sentence_428

Death from childhood cancer decreased by half between 1975 and 2010 in the United States. Cancer_sentence_429

History Cancer_section_40

Main article: History of cancer Cancer_sentence_430

Cancer has existed for all of human history. Cancer_sentence_431

The earliest written record regarding cancer is from circa 1600 BC in the Egyptian Edwin Smith Papyrus and describes breast cancer. Cancer_sentence_432

Hippocrates (c. 460 BC – c. 370 BC) described several kinds of cancer, referring to them with the Greek word karkinos (crab or crayfish). Cancer_sentence_433

This name comes from the appearance of the cut surface of a solid malignant tumor, with "the veins stretched on all sides as the animal the crab has its feet, whence it derives its name". Cancer_sentence_434

Galen stated that "cancer of the breast is so called because of the fancied resemblance to a crab given by the lateral prolongations of the tumor and the adjacent distended veins". Cancer_sentence_435

Celsus (c. 25 BC – 50 AD) translated karkinos into the Latin cancer, also meaning crab and recommended surgery as treatment. Cancer_sentence_436

Galen (2nd century AD) disagreed with the use of surgery and recommended purgatives instead. Cancer_sentence_437

These recommendations largely stood for 1000 years. Cancer_sentence_438

In the 15th, 16th and 17th centuries, it became acceptable for doctors to dissect bodies to discover the cause of death. Cancer_sentence_439

The German professor Wilhelm Fabry believed that breast cancer was caused by a milk clot in a mammary duct. Cancer_sentence_440

The Dutch professor Francois de la Boe Sylvius, a follower of Descartes, believed that all disease was the outcome of chemical processes and that acidic lymph fluid was the cause of cancer. Cancer_sentence_441

His contemporary Nicolaes Tulp believed that cancer was a poison that slowly spreads and concluded that it was contagious. Cancer_sentence_442

The physician John Hill described tobacco snuff as the cause of nose cancer in 1761. Cancer_sentence_443

This was followed by the report in 1775 by British surgeon Percivall Pott that chimney sweeps' carcinoma, a cancer of the scrotum, was a common disease among chimney sweeps. Cancer_sentence_444

With the widespread use of the microscope in the 18th century, it was discovered that the 'cancer poison' spread from the primary tumor through the lymph nodes to other sites ("metastasis"). Cancer_sentence_445

This view of the disease was first formulated by the English surgeon Campbell De Morgan between 1871 and 1874. Cancer_sentence_446

Society and culture Cancer_section_41

Although many diseases (such as heart failure) may have a worse prognosis than most cases of cancer, cancer is the subject of widespread fear and taboos. Cancer_sentence_447

The euphemism of "a long illness" to describe cancers leading to death is still commonly used in obituaries, rather than naming the disease explicitly, reflecting an apparent stigma. Cancer_sentence_448

Cancer is also euphemised as "the C-word"; Macmillan Cancer Support uses the term to try to lessen the fear around the disease. Cancer_sentence_449

In Nigeria, one local name for cancer translates into English as "the disease that cannot be cured". Cancer_sentence_450

This deep belief that cancer is necessarily a difficult and usually deadly disease is reflected in the systems chosen by society to compile cancer statistics: the most common form of cancer—non-melanoma skin cancers, accounting for about one-third of cancer cases worldwide, but very few deaths—are excluded from cancer statistics specifically because they are easily treated and almost always cured, often in a single, short, outpatient procedure. Cancer_sentence_451

Western conceptions of patients' rights for people with cancer include a duty to fully disclose the medical situation to the person, and the right to engage in shared decision-making in a way that respects the person's own values. Cancer_sentence_452

In other cultures, other rights and values are preferred. Cancer_sentence_453

For example, most African cultures value whole families rather than individualism. Cancer_sentence_454

In parts of Africa, a diagnosis is commonly made so late that cure is not possible, and treatment, if available at all, would quickly bankrupt the family. Cancer_sentence_455

As a result of these factors, African healthcare providers tend to let family members decide whether, when and how to disclose the diagnosis, and they tend to do so slowly and circuitously, as the person shows interest and an ability to cope with the grim news. Cancer_sentence_456

People from Asian and South American countries also tend to prefer a slower, less candid approach to disclosure than is idealized in the United States and Western Europe, and they believe that sometimes it would be preferable not to be told about a cancer diagnosis. Cancer_sentence_457

In general, disclosure of the diagnosis is more common than it was in the 20th century, but full disclosure of the prognosis is not offered to many patients around the world. Cancer_sentence_458

In the United States and some other cultures, cancer is regarded as a disease that must be "fought" to end the "civil insurrection"; a War on Cancer was declared in the US. Cancer_sentence_459

Military metaphors are particularly common in descriptions of cancer's human effects, and they emphasize both the state of the patient's health and the need to take immediate, decisive actions himself rather than to delay, to ignore or to rely entirely on others. Cancer_sentence_460

The military metaphors also help rationalize radical, destructive treatments. Cancer_sentence_461

In the 1970s, a relatively popular alternative cancer treatment in the US was a specialized form of talk therapy, based on the idea that cancer was caused by a bad attitude. Cancer_sentence_462

People with a "cancer personality"—depressed, repressed, self-loathing and afraid to express their emotions—were believed to have manifested cancer through subconscious desire. Cancer_sentence_463

Some psychotherapists said that treatment to change the patient's outlook on life would cure the cancer. Cancer_sentence_464

Among other effects, this belief allowed society to blame the victim for having caused the cancer (by "wanting" it) or having prevented its cure (by not becoming a sufficiently happy, fearless and loving person). Cancer_sentence_465

It also increased patients' anxiety, as they incorrectly believed that natural emotions of sadness, anger or fear shorten their lives. Cancer_sentence_466

The idea was ridiculed by Susan Sontag, who published Illness as Metaphor while recovering from treatment for breast cancer in 1978. Cancer_sentence_467

Although the original idea is now generally regarded as nonsense, the idea partly persists in a reduced form with a widespread, but incorrect, belief that deliberately cultivating a habit of positive thinking will increase survival. Cancer_sentence_468

This notion is particularly strong in breast cancer culture. Cancer_sentence_469

One idea about why people with cancer are blamed or stigmatized, called the just-world hypothesis, is that blaming cancer on the patient's actions or attitudes allows the blamers to regain a sense of control. Cancer_sentence_470

This is based upon the blamers' belief that the world is fundamentally just and so any dangerous illness, like cancer, must be a type of punishment for bad choices, because in a just world, bad things would not happen to good people. Cancer_sentence_471

Economic effect Cancer_section_42

The total health care expenditure on cancer in the US was estimated to be $80.2 billion in 2015. Cancer_sentence_472

Even though cancer-related health care expenditure have increased in absolute terms during recent decades, the share of health expenditure devoted to cancer treatment has remained close to 5% between the 1960s and 2004. Cancer_sentence_473

A similar pattern has been observed in Europe where about 6% of all health care expenditure are spent on cancer treatment. Cancer_sentence_474

In addition to health care expenditure and financial toxicity, cancer causes indirect costs in the form of productivity losses due to sick days, permanent incapacity and disability as well as premature death during working age. Cancer_sentence_475

Cancer causes also costs for informal care. Cancer_sentence_476

Indirect costs and informal care costs are typically estimated to exceed or equal the health care costs of cancer. Cancer_sentence_477

Workplace Cancer_section_43

In the United States, cancer is included as a protected condition by the Equal Employment Opportunity Commission (EEOC), mainly due to the potential for cancer having discriminating effects on workers. Cancer_sentence_478

Discrimination in the workplace could occur if an employer holds a false belief that a person with cancer is not capable of doing a job properly, and may ask for more sick leave than other employees. Cancer_sentence_479

Employers may also make hiring or firing decisions based on misconceptions about cancer disabilities, if present. Cancer_sentence_480

The EEOC provides interview guidelines for employers, as well as lists of possible solutions for assessing and accommodating employees with cancer. Cancer_sentence_481

Research Cancer_section_44

Main article: Cancer research Cancer_sentence_482

Because cancer is a class of diseases, it is unlikely that there will ever be a single "cure for cancer" any more than there will be a single treatment for all infectious diseases. Cancer_sentence_483

Angiogenesis inhibitors were once incorrectly thought to have potential as a "silver bullet" treatment applicable to many types of cancer. Cancer_sentence_484

Angiogenesis inhibitors and other cancer therapeutics are used in combination to reduce cancer morbidity and mortality. Cancer_sentence_485

Experimental cancer treatments are studied in clinical trials to compare the proposed treatment to the best existing treatment. Cancer_sentence_486

Treatments that succeeded in one cancer type can be tested against other types. Cancer_sentence_487

Diagnostic tests are under development to better target the right therapies to the right patients, based on their individual biology. Cancer_sentence_488

Cancer research focuses on the following issues: Cancer_sentence_489

Cancer_unordered_list_7

  • Agents (e.g. viruses) and events (e.g. mutations) that cause or facilitate genetic changes in cells destined to become cancer.Cancer_item_7_37
  • The precise nature of the genetic damage and the genes that are affected by it.Cancer_item_7_38
  • The consequences of those genetic changes on the biology of the cell, both in generating the defining properties of a cancer cell and in facilitating additional genetic events that lead to further progression of the cancer.Cancer_item_7_39

The improved understanding of molecular biology and cellular biology due to cancer research has led to new treatments for cancer since US President Richard Nixon declared the "War on Cancer" in 1971. Cancer_sentence_490

Since then, the country has spent over $200 billion on cancer research, including resources from public and private sectors. Cancer_sentence_491

The cancer death rate (adjusting for size and age of the population) declined by five percent between 1950 and 2005. Cancer_sentence_492

Competition for financial resources appears to have suppressed the creativity, cooperation, risk-taking and original thinking required to make fundamental discoveries, unduly favoring low-risk research into small incremental advancements over riskier, more innovative research. Cancer_sentence_493

Other consequences of competition appear to be many studies with dramatic claims whose results cannot be replicated and perverse incentives that encourage grantee institutions to grow without making sufficient investments in their own faculty and facilities. Cancer_sentence_494

Virotherapy, which uses convert viruses, is being studied. Cancer_sentence_495

Pregnancy Cancer_section_45

Cancer affects approximately 1 in 1,000 pregnant women. Cancer_sentence_496

The most common cancers found during pregnancy are the same as the most common cancers found in non-pregnant women during childbearing ages: breast cancer, cervical cancer, leukemia, lymphoma, melanoma, ovarian cancer and colorectal cancer. Cancer_sentence_497

Diagnosing a new cancer in a pregnant woman is difficult, in part because any symptoms are commonly assumed to be a normal discomfort associated with pregnancy. Cancer_sentence_498

As a result, cancer is typically discovered at a somewhat later stage than average. Cancer_sentence_499

Some imaging procedures, such as MRIs (magnetic resonance imaging), CT scans, ultrasounds and mammograms with fetal shielding are considered safe during pregnancy; some others, such as PET scans, are not. Cancer_sentence_500

Treatment is generally the same as for non-pregnant women. Cancer_sentence_501

However, radiation and radioactive drugs are normally avoided during pregnancy, especially if the fetal dose might exceed 100 cGy. Cancer_sentence_502

In some cases, some or all treatments are postponed until after birth if the cancer is diagnosed late in the pregnancy. Cancer_sentence_503

Early deliveries are often used to advance the start of treatment. Cancer_sentence_504

Surgery is generally safe, but pelvic surgeries during the first trimester may cause miscarriage. Cancer_sentence_505

Some treatments, especially certain chemotherapy drugs given during the first trimester, increase the risk of birth defects and pregnancy loss (spontaneous abortions and stillbirths). Cancer_sentence_506

Elective abortions are not required and, for the most common forms and stages of cancer, do not improve the mother's survival. Cancer_sentence_507

In a few instances, such as advanced uterine cancer, the pregnancy cannot be continued and in others, the patient may end the pregnancy so that she can begin aggressive chemotherapy. Cancer_sentence_508

Some treatments can interfere with the mother's ability to give birth vaginally or to breastfeed. Cancer_sentence_509

Cervical cancer may require birth by Caesarean section. Cancer_sentence_510

Radiation to the breast reduces the ability of that breast to produce milk and increases the risk of mastitis. Cancer_sentence_511

Also, when chemotherapy is given after birth, many of the drugs appear in breast milk, which could harm the baby. Cancer_sentence_512

Other animals Cancer_section_46

Veterinary oncology, concentrating mainly on cats and dogs, is a growing specialty in wealthy countries and the major forms of human treatment such as surgery and radiotherapy may be offered. Cancer_sentence_513

The most common types of cancer differ, but the cancer burden seems at least as high in pets as in humans. Cancer_sentence_514

Animals, typically rodents, are often used in cancer research and studies of natural cancers in larger animals may benefit research into human cancer. Cancer_sentence_515

In non-humans, a few types of transmissible cancer have been described, wherein the cancer spreads between animals by transmission of the tumor cells themselves. Cancer_sentence_516

This phenomenon is seen in dogs with Sticker's sarcoma (also known as canine transmissible venereal tumor), and in Tasmanian devils with devil facial tumour disease (DFTD). Cancer_sentence_517


Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Cancer.