Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body.[2][7] These contrast with benign tumors, which do not spread.[7] Possible signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained weight loss, and a change in bowel movements.[1] While these symptoms may indicate cancer, they can also have other causes.[1] Over 100 types of cancers affect humans.[7]

Other namesMalignant tumor, malignant neoplasm
A coronal CT scan showing a malignant mesothelioma
Legend: → tumor ←, ✱ central pleural effusion, 1 & 3 lungs, 2 spine, 4 ribs, 5 aorta, 6 spleen, 7 & 8 kidneys, 9 liver
SymptomsLump, abnormal bleeding, prolonged cough, unexplained weight loss, change in bowel movements[1]
Risk factorsExposure to carcinogens, tobacco, obesity, poor diet, lack of physical activity, excessive alcohol, certain infections[2][3]
TreatmentRadiation therapy, surgery, chemotherapy, targeted therapy[2][4]
PrognosisAverage five-year survival 66% (USA)[5]
Frequency24 million annually (2019)[6]
Deaths10 million annually (2019)[6]

Tobacco use is the cause of about 22% of cancer deaths.[2] Another 10% are due to obesity, poor diet, lack of physical activity or excessive drinking of alcohol.[2][8][9] Other factors include certain infections, exposure to ionizing radiation, and environmental pollutants.[3] 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).[2] These factors act, at least partly, by changing the genes of a cell.[10] Typically, many genetic changes are required before cancer develops.[10] Approximately 5–10% of cancers are due to inherited genetic defects.[11] Cancer can be detected by certain signs and symptoms or screening tests.[2] It is then typically further investigated by medical imaging and confirmed by biopsy.[12]

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, eating resistant starch,[13] vaccination against certain infectious diseases, limiting consumption of processed meat and red meat, and limiting exposure to direct sunlight.[14][15] Early detection through screening is useful for cervical and colorectal cancer.[16] The benefits of screening for breast cancer are controversial.[16][17] Cancer is often treated with some combination of radiation therapy, surgery, chemotherapy and targeted therapy.[2][4] Pain and symptom management are an important part of care.[2] Palliative care is particularly important in people with advanced disease.[2] The chance of survival depends on the type of cancer and extent of disease at the start of treatment.[10] In children under 15 at diagnosis, the five-year survival rate in the developed world is on average 80%.[18] For cancer in the United States, the average five-year survival rate is 66%.[5]

In 2015, about 90.5 million people worldwide had cancer.[19] In 2019, annual cancer cases grew by 23.6 million people and there were 10 million deaths worldwide, representing over the previous decade increases of 26% and 21%, respectively.[6][20]

The most common types of cancer in males are lung cancer, prostate cancer, colorectal cancer, and stomach cancer.[21] In females, the most common types are breast cancer, colorectal cancer, lung cancer, and cervical cancer.[10] If skin cancer other than melanoma were included in total new cancer cases each year, it would account for around 40% of cases.[22][23] In children, acute lymphoblastic leukemia and brain tumors are most common, except in Africa, where non-Hodgkin lymphoma occurs more often.[18] In 2012, about 165,000 children under 15 years of age were diagnosed with cancer.[21] The risk of cancer increases significantly with age, and many cancers occur more commonly in developed countries.[10] Rates are increasing as more people live to an old age and as lifestyle changes occur in the developing world.[24] The global total economic costs of cancer were estimated at US$1.16 trillion per year as of 2010.[25]

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