WASHINGTON – Colon cancer screening with sigmoidoscopy alone could miss up to 50% of colon polyps in older patients.
As people age, polyps seem to develop more and more proximally, Dr. Victor Tsirline said at the annual clinical congress of the American College of Surgeons. His review of more than 120,000 colonoscopies found that a flexible sigmoidoscopy alone could miss 44% of polyps in patients aged 60-69 years and 50% in those aged 70-79 years.
"We found that proximal colon polyps are more frequent with advanced age than previously considered," said Dr. Tsirline of Carolinas Medical Center, Charlotte, N.C. "So if this is true, what happens if we use sigmoidoscopy instead of colonoscopy? If we had, we would have missed 22,800 polyps, and 16,800 of those would have been adenomatous. In [patients 59 and younger] 32%-36% would be missed and in the older patients, 45%-50%."
Dr. Tsirline obtained his data from the Provation MD endoscopy transcription system. He obtained information on 120,365 colonoscopies that were performed from 2003 to 2011.
He cross-referenced this with CoPathPlus, a pathology reporting system. This allowed him to cross-reference polyp pathology (adenoma vs. hyperplasia) by computer algorithm. There was complete information available on 43,833 polyps.
Because of the large sample size, he set his level of statistical significance at P = less than 0.01.
The patients in the study were aged 20-90 years. Of the entire group of procedures, 53,492 colonoscopies (44%) identified polyps. Most studies (64%) found a single polyp; 25% found two, and 11% found three or more. A subset of the colonoscopies was only for average risk screening (44,806). Of these, 46% identified polyps.
Overall, 48% of polyps were adenomatous; 37% were hyperplastic. Pathology was not available for the remainder.
The polyps were fairly evenly distributed throughout the colon: rectum, 18%; sigmoid, 26%; descending, 14%; transverse, 16%; ascending, 15%; cecum, 11%.
However, when broken down by patient age, the distribution changed significantly. With every advancing decade of life, patients were:
• 22% less likely to have polyps in the rectum or sigmoid.
• 7% more likely to have polyps in the descending colon.
• 19% more likely to have polyps in the transverse colon.
• 30% more likely to have polyps in the ascending colon.
• 22% more likely to have polyps in the cecum.
All of these risks were statistically significant, and they held for both adenomatous and hyperplastic polyps.
The findings led Dr. Tsirline to conclude that flexible sigmoidoscopy should not be relied upon as an effective colon cancer screening method in patients older than 60 years. The U.S. Preventive Services Task Force states that sigmoidoscopy every 5 years combined with high-sensitivity fecal occult blood testing every 3 years is an adequate screening alternative.
"From this study, it’s pretty apparent that sigmoidoscopy should not be used for colon cancer screening in older patients," he said.
During a discussion, Dr. Tsirline fielded a question about screening the very elderly – patients in their 80s and 90s. The study group did include a small number of these patients, he said.
"I think the argument for not screening older individuals is based on the question of whether finding a colon cancer would change anything. Most people think the risks of screening and treatment would outweigh the benefits. Yes, you may find anything, but what are you going to do about it?"
Dr. Tsirline had no financial disclosures.