Colorectal Cancer Prevention and Screening

Colorectal cancer — cancer of the colon or rectum — is the second leading cause of cancer-related deaths in the United States. More than 148,000 new cases of colorectal cancer are expected to be diagnosed this year and more than 56,000 people will die from this disease.

Colorectal cancer, which affects men and women at equally frequent rates, develops from precancerous growths called polyps. Removing these polyps is the most effective way to prevent the development of colorectal cancer.


If you don't have a family history of colorectal cancer or polyps, the following is recommended for patients age 50 and older:

  • Fecal Occult Blood Test — This test, which looks for blood in the stool, is recommended annually. Polyps bleed more than normal tissue and these tiny amounts of blood can be detected by a test called hemocult.
  • Flexible Sigmoidoscopy — This is an exam of the lower section of the colon and rectum, where most polyps and cancers are located. This test is recommended every five years.
  • Colonoscopy — This an exam of the entire colon and rectum that is recommended every five to 10 years or when the fecal occult blood test or sigmoidoscopy is positive.

If you have a family history of colorectal cancer or polyps, your doctor may suggest a colonoscopy before age 50.


About 90 percent of colorectal cancers and deaths are thought to be preventable. In addition to regular colorectal cancer screenings, exercise and maintaining a healthy weight can reduce your risk of colorectal cancer.

To prevent colorectal cancer, the following is recommended:

  • Eat a well-balanced diet.
  • Reduce the fat you consume, particularly animal fat.
  • Increase your consumption of fruits and vegetables.
  • Exercise regularly.
  • Don't smoke.
  • Take a low dose aspirin a day. Aspirin can reduce the development of polyps, particularly in patients with previous history of polyps or colorectal cancer.
  • Take calcium supplements. Researchers believe calcium decreases the growth rate of polyps.


Reviewed by health care specialists at UCSF Medical Center.

This information is for educational purposes only and is not intended to replace the advice of your doctor or health care provider. We encourage you to discuss with your doctor any questions or concerns you may have.