Finding Polyps Missed During Colonoscopies for Lynch Syndrome
Posted by Kate Murphy on November 6th, 2008
Tags: colonoscopy, HNPCC, Lynch syndrome
Lynch syndrome (also known as hereditary nonpolyposis colon cancer) greatly increases the risk for colon and rectal cancer. People with the gene have about an 8 in 10 chance of getting colon cancer during their lives. Because Lynch cancers develop quickly and grow rapidly, it’s important to monitor people who carry the genes closely with colonoscopy every year or two.
When doctors in four research centers immediately followed up Lynch syndrome patients after a regular colonoscopy with more intense colonoscopy scrutiny, they discovered they had missed more polyps than they found. During the first exam, their miss rate for adenomas, polyps with the greatest risk of developing into cancer, was 55 percent.
In the study, patients with Lynch syndrome had a conventional colonoscopy and then were randomly assigned for an immediate follow-up test. One half had colonoscopies enhanced with a blue dye that makes polyps easier to see (chromoendoscopy). In the other group, doctors spent a longer time, more than 20 minutes, searching for polyps (intensive inspection).
- Fifty-four patients had an initial colonoscopy where 10 adenomas and 7 hyperplastic polyps were found and removed. Hyperplastic polyps are usually benign with little risk of becoming cancer. During the second exam, there were 12 more adenomas and 11 hyperplastic polyps.
- Twenty-eight patients had their colons sprayed with a blue dye during their follow-up exam. Fifteen more polyps — 5 adenomas and 11 hyperplastic – were found.
- Twenty-six patients had intensive inspections that lasted longer than regular colonoscopies. Doctors found 7 adenomas and 1 hyperplastic polyp.
Although more polyps were found with chromoendoscopy, when all factors were taken into consideration there was little difference between the adenomas uncovered between the two techniques. Chromoendoscopy takes longer than intensive inspection, about 30 minutes compared to 25 minutes to complete an intensive exam.
The researchers pointed out that this was a small pilot trial and that larger, randomized studies are necessary to show that chromoendoscopy will not, in fact, find more missed polyps.
Dr. Elena M. Stoffel, gastroenterologist at Brigham and Women’s Hospital in Boston, and her colleagues concluded,
Small adenomas are frequently missed in patients with Lynch syndrome. Although chromoendoscopy did not detect more missed adenomas than intensive inspection in this pilot study, larger trials are needed to determine optimal surveillance techniques in this high-risk population.
SOURCE: Stoffel et al.,Cancer Prevention Research, Volume 1, Number 6, November 1, 2008.
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