The risk of developing cancer
A multitude of factors, genetic and environmental, increase the risk of developing cancer.
Family history is an important factor. Some families have a much higher risk of developing certain cancers than others. For example, the risk of developing breast cancer in women increases from 1.5 to 3 times if the mother or sister had this type of cancer. Some breast cancers are linked to a specific gene mutation more common in some ethnic groups and in some families.
Women with this genetic mutation have between 80 and 90 percent chance of developing breast cancer and 40 to 50 percent of ovarian cancer. Researchers have found that one percent of Ashkenazi Jewish women have this genetic mutation. Many other cancers, including some types of skin cancer and colon cancer, also tend to affect entire families. People with chromosomal abnormalities have an increased risk of cancer.
For example, those with Down syndrome, which have three chromosomes instead of the usual two on the par-21, are 12 to 20 times greater risk of developing acute leukemia.
Environmental factors can also increase the risk of cancer. One of the most important task is to snuff, and that substantially increases the risk of developing cancers of the lung, mouth, larynx and bladder.
Another is the prolonged exposure to ultraviolet radiation, especially from the sun that causes skin cancer. Ionizing radiation, which are particularly carcinogenic, are used in X-rays are produced in nuclear reactors and atomic bomb explosions, and reach the Earth from space.
For example, survivors of the atomic bombs dropped on Hiroshima and Nagasaki during World War II have an increased risk of developing leukemia. The exposure of uranium miners has been linked to the development of lung cancer 15 or 20 years later. The risk increases much more if you also smoke miners. Exposure to ionizing radiation for a long time predisposes to cancer cells in blood, such as acute leukemia.
Diet is another important risk factor for cancer, particularly of the gastrointestinal system is affected. A diet high in fiber reduces the likelihood of developing colon cancer. A diet high in smoked and spicy foods increase the likelihood of developing stomach cancer. Current evidence suggests that a diet in which less than 30 percent of calories from fats reduces the risk of colon cancer, breast and possibly prostate cancer. Heavy drinkers of alcohol have a high risk of developing esophageal cancer.
It is well known that many chemicals cause cancer, presumably the same for many others. Exposure to certain chemicals commonly used can increase strongly, often years later, the possibility of developing a cancer. For example, exposure to asbestos can cause lung cancer and mesothelioma (cancer of the pleura). Cancer is more common in smokers who have been exposed to asbestos.
The risk of cancer also varies according to where you live. The risk of colon and breast cancer is low in Japan, but grows in the Japanese who have emigrated to the United States and reaches to match the rest of the American population. The Japanese have very high rates of stomach cancer. However, the incidence is lower in Japanese born in the United States. This geographic variation in cancer risk probably depends on many factors: a combination of genetics, diet and environment.
Several viruses are known to cause cancer in humans, and is suspected of several others. For example, the papillomavirus that causes genital warts is probably a cause of cervical cancer in women, CMV causes Kaposi’s sarcoma virus, hepatitis B can cause liver cancer, but has not yet been determined whether it is a carcinogen or a promoter. In Africa the Epstein-Barr virus causes Burkitt’s lymphoma, and in China causes cancers of the nose and pharynx. Obviously, you need some additional factor, either environmental or genetic, that this virus causes cancer. Some human retroviruses such as human immunodeficiency virus, causes lymphomas and other blood cancers.
Some parasites can cause cancer, is the case of Schistosoma (Bilharzia), which can cause bladder cancer by chronic irritation it. However, other causes of chronic irritation of the bladder does not cause cancer. Clonorchis infection, found mainly in the Far East, it can lead to cancer of the pancreas and bile ducts.
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