Colorectal Cancer: The Importance of Screening and Early Detection


Colorectal cancer is cancer that begins in the colon or the rectum. It is the third most common cancer among both men and women in the United States. This fact sheet answers some commonly asked questions about colorectal cancer screening.

Why Is Screening For Colorectal Cancer So Important?

Many colorectal cancers can be prevented through regular screening. Screening can find precancerous polyps— abnormal growths in the colon or rectum—so that they can be removed before they turn into cancer. Screening is crucial because when found early, colorectal cancer is highly treatable. Early stages of colorectal cancer usually present no symptoms, which tend to appear as the cancer progresses. The American Cancer Society recommends that colorectal cancer screening should start at age 45.

What Is a Colonoscopy?

A colonoscopy is the best screening test available for colorectal cancer. It is the only screening test that also prevents many colorectal cancers. Here are a few things you should know about this test:

  • During a colonoscopy, your doctor examines the lining of your entire colon to check for polyps or tumors. If any polyps are found, they can be removed immediately.
  • On the day of the colonoscopy, you will receive medication to help you relax. Most people fall asleep and do not remember much about the test when they wake up.
  • Your doctor performs a colonoscopy by inserting a long, thin, flexible tube called a colonoscope into your colon through the rectum. The tube has a tiny video camera and light at the end that sends images to a video monitor.
  • Before the procedure, you will receive instructions from your doctor on what to eat and how to empty your bowel.
  • Both men and women should have a colonoscopy starting at age 50. People at increased risk of colorectal cancer may start earlier, depending on your doctor’s instructions. (See “Risk Factors” on back). Also, your doctor will tell you in how many years you will need another colonoscopy.

Are Other Screening Tests Available?

If you are unable to have a colonoscopy, your doctor can give you information about the following tests and how often they should be performed:

  • Sigmoidoscopy
  • Double contrast barium enema
  • Virtual colonoscopy (CT colonoscopy)
  • Fecal occult blood test
  • DNA stool tests

You should note that these tests are not as thorough as a colonoscopy. If polyps or tumors are suspected based on these tests, you will still need to have a colonoscopy.

What Are Some of the Risk Factors For Colorectal Cancer?

A risk factor is anything that raises your chances of developing cancer. The following are some of the known risk factors for colorectal cancer. Talk with your doctor about your personal risk and how often you should be screened:

Age. Colorectal cancer is more common in people over the age of 50.

Personal and family history. People who have a parent, sibling or child with colorectal cancer are at a higher risk of developing it themselves, especially if the family member was diagnosed before the age of 60. People who have had colorectal cancer are at higher risk of another colorectal cancer.

Race. African-American men and women are at higher risk. The reasons for this are not fully understood.

Jews of eastern European descent. About 6% of American Jews who are of eastern European descent have DNA changes that increase their risk of colorectal cancer.

Inflammatory bowel disease (IBD). IBD, which includes ulcerative colitis and Crohn’s disease, puts you at a higher risk of developing colorectal cancer.

Lifestyle. Being overweight, having an inactive lifestyle, a diet high in red meat and processed meat, smoking, and heavy alcohol use can increase your risk of colorectal cancer.