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Cancer Risk factors
Scientists study risk factors and protective factors to find ways to prevent new cancers from starting. Anything that increases your chance of developing cancer is called a cancer risk factor; anything that decreases your chance of developing cancer is called a cancer protective factor.
Some risk factors for cancer can be avoided, but many cannot. For example, both smoking and inheriting certain genes are risk factors for some types of cancer, but only smoking can be avoided. Risk factors that a person can control are called modifiable risk factors.
Many other factors in our environment, diet, and lifestyle may cause or prevent cancer. This summary reviews only the major cancer risk factors and protective factors that can be controlled or changed to reduce the risk of cancer. Risk factors that are not described in the summary include certain sexual behaviors, the use of estrogen, and being exposed to certain substances at work or to certain chemicals.
Factors That are Known to Increase the Risk of Cancer
Cigarette Smoking and Tobacco Use
- Acute myelogenous leukemia (AML).
- Bladder cancer.
- Esophageal cancer.
- Kidney cancer.
- Lung cancer.
- Oral cavity cancer.
- Pancreatic cancer.
- Stomach cancer.
Not smoking or quitting smoking lowers the risk of getting cancer and dying from cancer. Scientists believe that cigarette smoking causes about 30% of all cancer deaths in the United States.
Certain viruses and bacteria are able to cause cancer. Viruses and other infection-causing agents cause more cases of cancer in the developing world (about 1 in 4 cases of cancer) than in developed nations (less than 1 in 10 cases of cancer). Examples of cancer-causing viruses and bacteria include:
- Human papillomavirus (HPV) increases the risk for cancers of the cervix, penis, vagina, anus, and oropharynx.
- Hepatitis B and hepatitis C viruses increase the risk for liver cancer.
- Epstein-Barr virus increases the risk for Burkitt lymphoma.
- Helicobacter pylori increases the risk for gastric cancer.
Two vaccines to prevent infection by cancer-causing agents have already been developed and approved by the U.S. Food and Drug Administration (FDA). One is a vaccine to prevent infection with hepatitis B virus. The other protects against infection with strains of human papillomavirus (HPV) that cause cervical cancer. Scientists continue to work on vaccines against infections that cause cancer.
Being exposed to radiation is a known cause of cancer. There are two main types of radiation linked with an increased risk for cancer:
- Ultraviolet radiation from sunlight: This is the main cause of nonmelanoma skin cancers.
- Ionizing radiation including:
Scientists believe that ionizing radiation causes leukemia, thyroid cancer, and breast cancer in women. Ionizing radiation may also be linked to myeloma and cancers of the lung, stomach, colon, esophagus, bladder, and ovary. Being exposed to radiation from diagnostic x-rays increases the risk of cancer in patients and x-ray technicians.
The risk of cancer after being exposed to ionizing radiation from diagnostic x-rays is higher for younger age groups than for older age groups, and is higher for women than for men. The risk of cancer also increases with the number of diagnostic x-rays a patient is given and the radiation dose per x-ray.
Immunosuppressive medicines are linked to an increased risk of cancer. These medicines lower the body's ability to stop cancer from forming. For example, immunosuppressive medicines may be used to keep a patient from rejecting an organ transplant.