These days most people have gotten the message about the importance of colorectal cancer screening: After we turn 50, nearly everyone ought to undergo a colonoscopy every 10 years. But say you're 79 and in good health with no family history of colon disease; do you really need another colonoscopy if you got one at 70? Probably not.

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Colonoscopies performed on Medicare recipients age 70 and older may be inappropriate. — Christie & Cole/Corbis

Turns out a number of older people are having these invasive, uncomfortable tests too often. New research shows that almost a quarter of the tests are performed on those who don't really need them.

On the other hand, while some older adults are being screened too often, other groups are not getting screened enough. Underscreening remains a problem for racial and ethnic minorities and those in lower socioeconomic populations.

A valuable test

During a colonoscopy, a doctor can find and remove precancerous polyps before they grow and spread. But colonoscopies are invasive procedures that carry small but real risks, such as bleeding, bowel perforations or complications from sedation, particularly in older people.

Groups like the U.S. Preventive Services Task Force (USPSTF), the American Cancer Society and the American College of Gastroenterology agree that routine screening colonoscopies should be carried out every 10 years starting at age 50.

Colorectal cancer is the third most commonly diagnosed cancer among men and women and the second leading cause of cancer death. An estimated 143,000 new cases will be diagnosed this year, according to the National Cancer Institute, and nearly 51,000 people will die from the disease. But the five-year survival rate is about 90 percent if it is caught early, which is why cancer screening is highly recommended.

The USPSTF says screening colonoscopies should be performed on a case-by-case basis for people between the ages of 76 and 85, and it recommends no screening for people over age 85. The benefit of early cancer detection in very old people is offset by the risk of complications.

But some doctors and patients aren't getting the message. A recent study published in JAMA Internal Medicine suggests that almost a quarter of colonoscopies are either performed too often or given to patients who are too old to benefit.

"It looks like some patients are getting screened inappropriately," says Kristin Sheffield, Ph.D., an epidemiologist at the University of Texas Medical Branch in Galveston who led the study.

The study didn't fault colonoscopies doctors performed because a patient had a problem or worrisome symptom, such as blood in the stool or abdominal pain. Nor does it address colonoscopies to check patients who previously have had colorectal cancer or precancerous growths. The remaining colonoscopies were classified as potentially inappropriate when they were performed in people over the age of 76, or if they were carried out less than 10 years after a previous normal colonoscopy.

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