Confused about colorectal cancer screening? We’ve got answers.

Most colorectal cancer cases are preventable. And the best way to prevent the disease is to be screened.

Before you learn about how often you should be screened, it’s important to understand the different kinds of screening tests you might need.

Tests that find colorectal cancer

Some tests are designed to find cancer, while others can uncover both cancer and polyps that might turn cancerous. They are:

Colonoscopy: Your healthcare provider will insert a thin, flexible tube with a light and video camera on it through the rectum into the entire length of the colon. Polyps can be removed during this procedure.

CT colonography (also known as virtual colonoscopy): X-rays and computers create an image of your entire colon.

Flexible sigmoidoscopy: This is similar to a colonoscopy, but it reaches only the lower third of the colon.

Double contrast barium enema: A liquid containing barium is put into your rectum, and then your colon is X-rayed. The liquid makes it easier to see your colon and rectum on an X-ray and helps show potential abnormalities.

Fecal occult blood test (FOBT) or fecal immunochemical test (FIT): These tests detect blood in the stool. Using a test kit from your provider, you will provide a small amount of stool, which is then tested.

Stool DNA tests: You’ll provide a stool sample, which is mailed to a lab that tests for DNA changes that might indicate cancer.

Screening recommendations

How often a person gets screenings, and which ones should be given, depend on a person’s likelihood of getting colon cancer. Those at high risk have:

• History of colorectal cancer or precancerous polyps.
• History of inflammatory bowel disease such as ulcerative colitis or Crohn’s disease.
• Family history of colorectal cancer or polyps.
• Family history of hereditary colorectal cancer syndrome.

Those at high risk should talk with their doctor about a personalized testing schedule; they might need to be tested before age 50 and be tested more often.

For those not at a high risk, screening should begin at age 50. The American Cancer Society recommends:

• A colonoscopy every 10 years; or CT colonography, flexible sigmoidoscopy or double-contrast barium enema every five years.
• A fecal test every year, or a fecal DNA test every three years.