Colonoscopies carry risks for older colon cancer survivors, study says

After age 75, recurrences of colon cancer are rare and the risks of repeated colonoscopies may outweigh the benefits, according to new research.

“Our study was different in that we specifically examined patients that were undergoing surveillance examinations because of a previous history of colonic polyps or cancer,” said lead author Dr. An Hong Tran of Kaiser Permanente Los Angeles Medical Center in California.

“We found that recurrent colorectal cancer in this population was significantly less likely after age 75,” Tran said. “We also found that the risk of post-procedure hospitalization following a surveillance colonoscopy increased significantly after age 75 compared to younger patients, even after adjusting for the effects of chronic illnesses.”

People with colorectal cancer or high-risk polyps usually undergo repeat colonoscopies every few years to make sure the disease hasn't recurred.

The Unites States Preventive Services Task Force recommends that most people start having regular colon cancer screening, including colonoscopies, at age 50, and if nothing seems amiss by age 75, the decision on whether to continue screening should be made on an individual basis.

The American College of Physicians recommends that screening stop after age 75.

But for a very specific group of patients – those who have had colon cancer or suspicious polyps – it’s recommended they continue to get regular “surveillance” colonoscopies indefinitely.

For the new study, Tran’s team wanted to assess the risks and benefits of surveillance screening in older patients by looking at the number of cancer recurrences and the rate of adverse effects of screening. They defined these as hospitalizations within 30 days of the surveillance colonoscopy.

The researchers included a group of nearly 5,000 people over age 75 with a history of colorectal cancer or suspicious polyps who had colonoscopies between 2001 and 2010 in the Kaiser Permanente health system. They compared this group to almost 23,000 younger patients aged 50 to 74 with similar histories, who underwent surveillance colonoscopies during the same period.

Of a total 373 colon cancers detected over the nine-year period, only five were found among the older patients, the authors report in JAMA Internal Medicine.

But hospitalization within 30 days after the colonoscopy was much more common in the elderly group, 527 of whom were hospitalized compared to 184 of the younger patients. As age increased, hospitalizations became more likely.

The researchers calculated that the older patients were about 28 percent more likely to be hospitalized after surveillance screening than the younger patients.

Post-screening problems included issues directly related to the procedure, such as gastrointestinal bleeding, perforation or arrhythmia, which together accounted for 13 percent of hospitalizations. Another 33 percent were for GI problems not directly procedure-related and 30 percent were for non-GI problems.

Post-procedure hospitalization is not necessarily life threatening, but can be serious, Tran said.

These new results apply only to surveillance colonoscopies, said Dr. Sidney Winawer, a gastroenterologist at Memorial Sloan Kettering Cancer Center in New York.

They should not be applied to the issue of general colonoscopy screening, which is a separate issue, he told Reuters Health.

“It’s an important distinction to make since screening uncovers a lot more disease than surveillance,” Winawer said. “In surveillance the disease has already been detected and removed.”

Colon cancer recurrence is very rare, and if it does recur it would probably be metastatic in a different area of the body, he noted.

Even so, only catching five cancers in the elderly group seems like a very low number, he said, and the subsequent hospitalization rate was high.

“The actual (number of) complications directly related to colonoscopy was small,” he said. “For the others, perhaps colonoscopy threw physiology off balance as can happen for older people.

“We don’t want to let this produce an aura of danger around colonoscopies,” Winawer said.

Surveillance colonoscopies should not be withheld, but should be used conservatively, and doctors always need to use their judgment on the benefits and risks of a procedure in an individual patient, Winawer said.