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School of Medicine
Colon Cancer Screening: What You Need to Know
Colon cancer is the second leading cause of cancer death in the United States today. It’s a serious American health problem, says Johns Hopkins gastroenterologist Francis Giardiello, M.D.
However, there are many ways you can decrease your risk or even prevent colon cancer. The single best thing you can do to prevent colon cancer is to get screened.
Giardiello breaks down what you should know about the colon cancer screening options available today.
Q. Why is colon cancer screening important?
A. Colon cancer develops from a small polyp that occurs in the lining of the colon. That small polyp slowly grows larger and larger. Once large enough, that polyp develops cancer and starts to spread.
It's important to remember the process of polyp to cancer takes about 10 years to occur. That’s plenty of time to get a screening to catch it — and get rid of it — before it turns to cancer.
Think of a polyp as a mushroom sitting on a stalk (your intestine’s lining). If a doctor identifies it on a colonoscopy, he or she can easily put a lasso (or a loop) around the stalk and cut off the mushroom. No mushroom means no cancer.
Q. How do you screen for colon cancer?
There’s more than one way to be screened for colon cancer today.
These options include:
• Colonoscopy: Before a colonoscopy, you’ll be asked to prep your bowel by drinking a liquid that helps clear out your colon. Then, doctors use a scope that has a camera attached to one end to examine inside your colon for polyps or cancer. Because the scope movement can cause discomfort, you’ll be sedated during the procedure. If a polyp is found, your doctor can remove it at the same time.
• Fecal occult blood test: This test looks for blood in your stool. You place a small bowel movement sample on a provided card and send it to a lab, where it is tested for blood. If blood is detected, your doctor might recommend you get a colonoscopy for further testing.
• Fecal immuno testing: This is similar to fecal occult testing, except you place the bowel movement sample in tubes. Depending on the results, you may require further testing.
• Sigmoidoscopy: A sigmoidoscope is another type of scope that only looks at the bottom third of the colon, where 60 percent of cancers occur.
• Barium enema: During this test, barium liquid is placed in the rectum through an enema, and then an X-ray is taken. The barium highlights any polyps or cancer for the doctor viewing the X-ray.
• Virtual colonoscopy: You undergo a CT scan that takes a detailed picture of the colon.
• Stool gene testing: This is a newer type of stool sample screening. Instead of testing for blood, the lab looks for certain gene changes that can indicate colon cancer.
Q. How do you know which screening is right for you?
A. Many physicians recommend most healthy people get a colonoscopy every 10 years starting at age 50 — that’s when most colon cancers start to develop. A colonoscopy is the most effective way doctors identify colon cancer.
Each type of screening has its own pros and cons. Your doctor can provide more information on screening options and recommend which is best for you based on several factors, including your:
- Family history
- Overall health