Diseases

Cancer Prevention Information

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.

Carcinogenesis

Carcinogenesis is the process in which normal cells turn into cancer cells. Carcinogenesis is the series of steps that take place as a normal cell becomes a cancer cell. Cells are the smallest units of the body and they make up the body's tissues. Each cell contains genes that guide the way the body grows, develops, and repairs itself. There are many genes that control whether a cell lives or dies, divides (multiplies), or takes on special functions, such as becoming a nerve cell or a muscle cell. Changes (mutations) in genes occur during carcinogenesis. Changes (mutations) in genes can cause normal controls in cells to break down. When this happens, cells do not die when they should and new cells are produced when the body does not need them. The buildup of extra cells may cause a mass (tumor) to form. Tumors can be benign or malignant (cancerous). Malignant tumor cells invade nearby tissues and spread to other parts of the body. Benign tumor cells do not invade nearby tissues or spread.

Factors That are Known to Increase the Risk of Cancer

Cigarette Smoking and Tobacco Use Tobacco use is strongly linked to an increased risk for many kinds of cancer. Smoking cigarettes is the leading cause of the following types of cancer:

• Acute myelogenous leukemia (AML).
• Bladder cancer.
• Esophageal cancer.
• Kidney cancer.
• Lung cancer.
• Oral cavity cancer.
• Pancreatic cancer.
• Stomach cancer.

• 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.

• Ultraviolet radiation from sunlight: This is the main cause of nonmelanoma skin cancers.
• Ionizing radiation including:
• Medical radiation from tests to diagnose cancer such as x-rays, CT scans, fluoroscopy, and nuclear medicine scans.
• Radon gas in our homes.

Factors That May Affect the Risk of Cancer

Diet The foods that you eat on a regular basis make up your diet. Diet is being studied as a risk factor for cancer. It is hard to study the effects of diet on cancer because a person's diet includes foods that may protect against cancer and foods that may increase the risk of cancer. It is also hard for people who take part in the studies to keep track of what they eat over a long period of time. This may explain why studies have different results about how diet affects the risk of cancer. Some studies show that fruits and nonstarchy vegetables may protect against cancers of the mouth, esophagus, and stomach. Fruits may also protect against lung cancer. Some studies have shown that a diet high in fat, proteins, calories, and red meat increases the risk of colorectal cancer, but other studies have not shown this. It is not known if a diet low in fat and high in fiber, fruits, and vegetables lowers the risk of colorectal cancer. Alcohol Studies have shown that drinking alcohol is linked to an increased risk of the following types of cancers:

• Oral cancer.
• Esophageal cancer.
• Breast cancer.
• Colorectal cancer (in men).

• Postmenopausal breast cancer.
• Colorectal cancer.
• Endometrial cancer.
• Esophageal cancer.
• Kidney cancer.
• Pancreatic cancer.

• Links between air pollution and cancer risk have been found. These include links between lung cancer and secondhand tobacco smoke, outdoor air pollution, and asbestos.
• Drinking water that contains a large amount of arsenic has been linked to skin, bladder, and lung cancers.

Interventions that are known to lower cancer risk

An intervention is a treatment or action taken to prevent or treat disease, or improve health in other ways. Many studies are being done to find ways to keep cancer from starting or recurring (coming back). Chemoprevention is being studied in patients who have a high risk of developing cancer. Chemoprevention is the use of substances to lower the risk of cancer, or keep it from recurring. The substances may be natural or made in the laboratory. Some chemopreventive agents are tested in people who are at high risk for a certain type of cancer. The risk may be because of a precancerous condition, family history, or lifestyle factors. Some chemoprevention studies have shown good results. For example, selective estrogen receptor modulators (SERMS) such as tamoxifen or raloxifene have been shown to reduce the risk of breast cancer in women at high risk. Finasteride and dutasteride have been shown to reduce the risk of prostate cancer. New ways to prevent cancer are being studied in clinical trials. Chemoprevention agents that are being studied in clinical trials include COX-2 inhibitors. They are being studied for the prevention of colorectal and breast cancer. Aspirin is being studied for the prevention of colorectal cancer.

Interventions that are not known to lower cancer risk

Vitamin and dietary supplements have not been shown to prevent cancer. An intervention is a treatment or action taken to prevent or treat disease, or improve health in other ways. There is not enough proof that taking multivitamin and mineral supplements or single vitamins or minerals can prevent cancer. The following vitamins and mineral supplements have been studied, but have not been shown to lower the risk of cancer:

• Vitamin B6.
• Vitamin B12.
• Vitamin E.
• Vitamin C.
• Beta carotene.
• Folic acid.
• Selenium.
• Vitamin D.