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Nearly 15 percent of colorectal cancers are diagnosed in people under age 50, suggesting that it might be beneficial to begin regular screenings — including, perhaps, the dreaded colonoscopy — earlier than is customary, according to a study published Monday in the journal Cancer.

The American Cancer Society calls for regular colon cancer screening  — which could involve analysis of stool samples or barium enemas, in addition to the colonoscopy — to begin at age 50 in most cases, except for people who have had close relatives diagnosed with colon cancer.

But Dr. Samantha Hendren, who coauthored the paper, said those guidelines might cause doctors to miss a significant number of ill patients.


“I have had patients under 50 coming to me, saying, ‘I’ve had symptoms for a year,’ and their doctors told them it was nothing to worry about,” said Hendren,  a cancer researcher at the University of Michigan. “My hope is that this paper will spur epidemiological research on the cost versus the benefit of testing sooner.”

But encouraging more screening tests, for any type of disease, requires a careful analysis of the potential gains, especially in an era of mounting concern about the high cost of over-testing. Setting age guidelines can be both contentious and emotional; breast cancer experts have not been able to agree, for instance, on a common set of recommendations for mammograms.


For their study, Hendren and her colleagues studied nearly 40,000 colorectal cancer patients whose average age at diagnosis was 42 and compared them to older patients.

Nearly 15 percent of the younger patients were African-American, compared to 12 percent of the patients over 50. The younger patients were also more likely to be Asian, Pacific Islander, or Native American.

But the larger differences came with the severity of the disease. In 65 percent of the younger patients, the colon cancer had spread by the time of diagnosis. That had happened with fewer than 58 percent of the older patients.

The good news is that the younger patients had higher five-year survival rates, particularly when the cancer was treated aggressively. This was true even for advanced colorectal cancer, which had a survival rate of 21 percent for the younger patients, compared to 14 percent for the older patients.

A study released last week from the University of Colorado Cancer Center found that colorectal cancers in younger patients have different genetic drivers than those in older patients. That may explain why the cancer tends to be more aggressive in patients under 50.