Colorectal Cancer

Screening | Prevention | Additional Resources

Prevention
  • About
  • Risk Factors
  • Lowering Risk

Cancer prevention is action taken to lower the chance of getting cancer. By preventing cancer, the number of new cases of cancer in a group or population is lowered. Hopefully, this will lower the number of deaths caused by cancer.

To prevent new cancers from starting, scientists look at risk factors and protective factors. 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. Regular exercise and a healthy diet may be protective factors for some types of cancer. Avoiding risk factors and increasing protective factors may lower your risk, but it does not mean that you will not get cancer.

Different ways to prevent cancer are being studied, including:

  • Changing lifestyle or eating habits.

  • Avoiding things known to cause cancer.

  • Taking medicines to treat a precancerous condition or to keep cancer from starting.

Colorectal cancer is a disease in which malignant (cancer) cells form in the tissues of the colon or the rectum.

The colon is part of the body's digestive system. The digestive system removes and processes nutrients (vitamins, minerals, carbohydrates. fats, proteins, and water) from foods and helps pass waste material out of the body. The digestive system is made up of the mouth, throat, esophagus, stomach, and the small and large intestines. The first 6 feet of the large intestine are called the large bowel or colon. The last 6 inches are the rectum and the anal canal. The anal canal ends at the anus (the opening of the large intestine to the outside of the body).

Cancer that begins in the colon is called colon cancer, and cancer that begins in the rectum is called rectal cancer. Cancer that affects either of these organs may also be called colorectal cancer.

Colorectal cancer is the second leading cause of death from cancer in the United States.

The number of new colorectal cancer cases and the number of deaths from colorectal cancer are decreasing a little bit each year.

Finding and treating colorectal cancer early may prevent death from colorectal cancer. Screening tests may be used to help find colorectal cancer. See the PDQ summary on Screening for Colorectal Cancer for more information.

Avoiding risk factors and increasing protective factors may help prevent colorectal cancer.

Most people with a certain risk factor for cancer do not actually get the disease. Doctors cannot always explain why one person gets cancer and another does not. Talk to your doctor or other health care professional about cancer prevention methods that might help you.

The following risk factors may increase the risk of colorectal cancer:Age

The risk of colorectal cancer begins to increase after age 40 and continues to increase as you get older.

Obesity and lack of exercise

Obesity is linked to an increased risk of colorectal cancer. A lifestyle that does not include regular exercise may also be linked to an increased risk of colorectal cancer.

Smoking

Smoking cigarettes is linked to an increased risk of developing colorectal adenomas (noncancerous tumors) and colorectal cancer. Cigarette smokers who have had surgery to remove colorectal adenomas have an increased risk for the adenomas to recur (come back).

Alcohol

Drinking alcoholic beverages may increase the risk of colorectal cancer.

The following protective factors may decrease the risk of colorectal cancer:Hormone replacement therapy

Studies have shown that hormone replacement therapy (HRT) that includes both estrogen and progesterone lowers the risk of colorectal cancer in postmenopausal women. HRT with estrogen alone does not lower the risk. However, hormone use may increase the risk of breast cancer, heart disease, and blood clots.

Polyp removal

Most colorectal polyps are adenomas, which may develop into cancer. The removal of polyps in the colon and rectum may lower the risk of colorectal cancer. Bleeding and infection sometimes occur after polyps are removed during colonoscopy or sigmoidoscopy.

The effect of the following factors on the risk of colorectal cancer is not known:

Nonsteroidal anti-inflammatory drugs (NSAIDs)

It is not known if the use of nonsteroidal anti-inflammatory drugs (such as aspirin, ibuprofen, and naproxen) lowers the risk of colorectal cancer. Studies have shown that nonsteroidal anti-inflammatory drugs (NSAIDs) lower the risk of colorectal adenomas (noncancerous tumors), but it is not clear if this results in a lower risk of cancerous tumors in the colon and rectum. The use of NSAIDs increases the risk of heart attack and stroke and some can cause bleeding in the stomach and intestines.

Vitamins

It is not known if taking vitamin D or high doses of folic acid lowers the risk of colorectal cancer.

Diet

It is not known if a diet low in fat and high in fiber, fruits, and vegetables lowers the risk of colorectal cancer.

Some studies have shown that a diet high in fat, proteins, calories, and meat increases the risk of colorectal cancer, but other studies have not.

For more information on diet and health, see the Fruits and Veggies website.

Statins

Studies have not shown that taking statins (cholesterol-lowering drugs) affects the risk of colorectal cancer.

Cancer prevention clinical trials are used to study ways to prevent cancer.

Cancer prevention clinical trials are used to study ways to lower the risk of developing certain types of cancer. Some cancer prevention trials are conducted with healthy people who have not had cancer but who have an increased risk for cancer. Other prevention trials are conducted with people who have had cancer and are trying to prevent another cancer of the same type or to lower their chance of developing a new type of cancer. Other trials are done with healthy volunteers who are not known to have any risk factors for cancer.

The purpose of some cancer prevention clinical trials is to find out whether actions people take can prevent cancer. These may include exercising more or quitting smoking or taking certain medicines, vitamins, minerals, or food supplements.

New ways to prevent colorectal cancer are being studied in clinical trials.

Clinical trials are taking place in many parts of the country. Information about clinical trials can be found in the Clinical Trials section of the NCI Web site. Check NCI's PDQ Cancer Clinical Trials Registry for colon cancer prevention trials or rectal cancer prevention trials that are now accepting patients.

Cancer information from the NCI PDQ service