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Colorectal Cancer Prevention (PDQ®)

Last Modified: 04/14/2014

What is prevention?

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.

General Information About Colorectal Cancer

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).

Enlarge Gastrointestinal (digestive) system anatomy; shows esophagus, liver, stomach, colon, small intestine, rectum, and anus.
Anatomy of the lower digestive system, showing the colon and other organs.


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.

See the following PDQ summaries for more information about 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 both decreasing a little bit each year. However, in adults younger than 50 years, the number of new colorectal cancer cases has slowly increased since 1998.

Finding and treating colorectal cancer early may prevent death from colorectal cancer. Screening tests may be used to help find colorectal cancer.

Colorectal Cancer Prevention

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

Avoiding cancer risk factors may help prevent certain cancers. Risk factors include smoking, being overweight, and not getting enough exercise. Increasing protective factors such as quitting smoking, eating a healthy diet, and exercising may also help prevent some cancers. Talk to your doctor or other health care professional about how you might lower your risk of cancer.

The following risk factors increase the risk of colorectal cancer:

Age

The risk of colorectal cancer increases after age 50. Most cases of colorectal cancer are diagnosed after age 50.

Family history of colorectal cancer

Having a parent, brother, sister, or child with colorectal cancer doubles a person's risk of colorectal cancer.

Personal history

Having a personal history of inflammatory bowel disease increases the risk of colorectal cancer.

Inherited risk

The risk of colorectal cancer is increased when certain gene changes linked to familial adenomatous polyposis (FAP) or hereditary nonpolyposis colon cancer (HNPCC or Lynch Syndrome) are inherited.

Alcohol

Drinking 3 or more alcoholic beverages per day increases the risk of colorectal cancer. Drinking alcohol is also linked to the risk of forming large colorectal adenomas (benign tumors).

Cigarette smoking

Cigarette smoking is linked to an increased risk of colorectal cancer and death from colorectal cancer.

Smoking cigarettes is also linked to an increased risk of forming colorectal adenomas. Cigarette smokers who have had surgery to remove colorectal adenomas are at an increased risk for the adenomas to recur (come back).

Obesity

Obesity is linked to an increased risk of colorectal cancer and death from colorectal cancer.

The following protective factors decrease the risk of colorectal cancer:

Physical activity

A lifestyle that includes regular physical activity is linked to a decreased risk of colorectal cancer.

Aspirin

Taking aspirin every day for at least 5 years decreases the risk of colorectal cancer and the risk of death from colorectal cancer. In a study of women, taking aspirin every other day for 10 years decreased the risk of colorectal cancer.

The possible harms of aspirin use include a higher than normal risk of bleeding in the stomach, intestines, or brain.

Combination hormone replacement therapy

Studies have shown that combination hormone replacement therapy (HRT) that includes both estrogen and progesterone lowers the risk of invasive colorectal cancer in postmenopausal women. However, combination HRT does not lower the risk of dying from colorectal cancer.

Not all hormone replacement therapy decreases the risk of having colorectal cancer. HRT with estrogen alone does not lower the risk of having invasive colorectal cancer or the risk of dying from colorectal cancer.

The possible harms of hormone replacement therapy include an increased risk of having:

Polyp removal

Most colorectal polyps are adenomas, which may develop into cancer. Removing colorectal polyps that are larger than 1 centimeter (cm) may lower the risk of colorectal cancer. It is not known if removing smaller polyps lowers the risk of colorectal cancer.

The possible harms of polyp removal during colonoscopy or sigmoidoscopy include a tear in the wall of the colon and bleeding.

Enlarge Colon polyps; shows two polyps (one flat and one pedunculated) inside the colon.  Inset shows photo of a pedunculated polyp.
Polyps in the colon. Some polyps have a stalk and others do not. Inset shows a photo of a polyp with a stalk.

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

Nonsteroidal anti-inflammatory drugs (NSAIDs) other than aspirin

It is not known if the use of nonsteroidal anti-inflammatory drugs or NSAIDs (such as celecoxib, naproxen, and ibuprofen) lowers the risk of colorectal cancer.

Studies have shown that taking the nonsteroidal anti-inflammatory drug celecoxib reduces the risk of colorectal adenomas (benign tumors) coming back after they have been removed. It is not clear if this results in a lower risk of cancerous tumors in the colon and rectum. Taking celecoxib also has been shown to reduce the number of polyps that form in the colon and rectum of patients with familial adenomatous polyposis (FAP).

The possible harms of NSAIDs include:

Diet

It is not known if a diet low in fat and meat 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 Nutrition for Everyone: Fruits and Vegetables Web site.

Vitamins

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

Calcium

It is not known if taking calcium supplements lowers the risk of colorectal cancer.

Taking medicine to reduce cholesterol levels does not affect the risk of colorectal cancer.

Studies have shown that taking statins (cholesterol -lowering drugs) does not increase or decrease 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 list of cancer clinical trials for colon cancer prevention trials or rectal cancer prevention trials that are now accepting patients.

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