What is Cancer?
Cancer is a group of diseases that involve abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread to other parts of the body.
Possible signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained weight loss, and a change in bowel movements. While these symptoms may indicate it, they may have other causes. More than 100 types of cancer affect humans.
Tobacco use is the cause of around 22% of deaths from cancer. Another 10% is due to obesity, poor diet, lack of physical activity and excessive consumption of alcohol. Other factors include certain infections, exposure to ionizing radiation and environmental pollutants. In the developing world, 15% of this disease is due to infections such as Helicobacter pylori, hepatitis B, hepatitis C, human papillomavirus infection, Epstein-Barr virus and human immunodeficiency virus.
These factors act, at least in part, by changing the genes of a cell. Normally, many genetic changes are required before it develops. Approximately 5-10% of cancers are due to genetic defects inherited from a person’s parents. It can be detected by certain signs and symptoms or screening tests. Then, it is typically investigated more thoroughly by medical images and confirmed by a biopsy.
Many cancers can be prevented by not smoking, maintaining a healthy weight, not drinking too much alcohol, eating lots of vegetables, fruits and whole grains, vaccinating against certain infectious diseases, not eating too much processed and red meat, and avoiding too much exposure to sunlight. Early detection through screening is useful for cervical and colorectal cancer. The benefits of screening for breast cancer are controversial. It is often treated with some combination of radiation therapy, surgery, chemotherapy and targeted therapy.
Pain and symptom management are an important part of care. Palliative care is particularly important for people with advanced disease. The probability of survival depends on the type of cancer and the degree of the disease at the beginning of treatment. In children under 15 years old at the time of diagnosis, the five-year survival rate in the developed world is, on average, 80%. For cancer in the United States, the average five-year survival rate is 66%.
In 2015, around 90.5 million people had this disease. About 14.1 million new cases occur annually (not including skin cancer other than melanoma). It caused about 8.8 million deaths (15.7% of deaths). The most common cancer types in men are lung cancer, prostate cancer, colorectal cancer and stomach cancer. In women, the most common types are breast cancer, colorectal cancer, lung cancer and cervical cancer. If skin cancer other than melanoma were included in the total number of new cancers each year, it would account for about 40% of the cases.
In children, acute lymphoblastic leukemia and brain tumors are more common, except in Africa, where non-Hodgkin’s lymphoma occurs most often. In 2012, around 165,000 children under the age of 15 were diagnosed with it. The risk of cancer increases significantly with age and many cancers occur more commonly in developed countries. Rates are increasing as more people live to old age and when lifestyle changes occur in the developing world. The financial costs of cancer were estimated at $1.16 trillion per year as of 2010.