Q&A: Screening for Colorectal Cancer

Q: I just turned 50 and my doctor is recommending that I have a colonoscopy and/or a fecal occult blood test to see if I have colorectal cancer. Do you think either one of these tests is worth having?

A: Most physicians recommend colonoscopy and/or the fecal occult blood test for patients age 50 or older. They use the fecal occult blood test to determine if there’s any hidden blood in the stool. In the case of colonoscopy, they’re looking for colorectal adenomatous polyps, benign tumors that affect about a quarter of the people in this age bracket. Nearly all cases of colorectal cancer, which kills approximately 50,000 Americans every year, develop from these polyps.

When it comes to cancer screening, I hesitate to make blanket recommendations. However, before you have any test done, I strongly encourage you to understand both the pros—the slim but potentially lifesaving possibility that early-stage, clinically significant cancer will be found and treated—and the cons—the high risk of false positives, additional testing, anxiety, and unnecessary treatment. That way, you’ll be better prepared to deal with the outcome, whatever it may be.

Beyond that, with regard to fecal occult blood tests and colonoscopies, here are some other things to keep in mind.

Three randomized studies suggest that fecal occult blood tests lower chances of dying from colon cancer by 15 to 30 percent. However, false positives are very common. And false findings often lead to repeat testing, unneeded therapies, and invasive surgical procedures to double-check results.

For maximum accuracy, you should avoid red meat, aspirin, and large amounts of vitamin C before a fecal occult blood test, since they can cause small amounts of blood to appear in the stool. Also eat a high-fiber diet for 72 hours before the test.

Regarding colonoscopy, the Preventive Services Task Force has concluded, “It is unclear whether the increased accuracy of colonoscopy…offsets the procedure’s additional complications, inconvenience, and costs.”

I understand that this is an emotionally charged issue. Cancer is scary and the treatments for it are as frightening as the disease itself. If you have symptoms of cancer, the tests are probably a good idea. Otherwise, think twice. Doctors sometimes suggest these tests for all the wrong reasons: fears of malpractice, financial incentives, and even patient demand.

Bottom line: Your best bet is to talk to your doctor about what course would be recommended if the results were positive, consider what you have learned here, and make your own educated decision. — JW

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