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Shorter Colonoscopy Withdrawal Times Increased Interval Cancer Risk
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PHILADELPHIA — Shorter withdrawal times during screening colonoscopies were associated with increased risk for interval colorectal cancer, and longer withdrawal times were associated with increased adenoma detection rates, according to data presented at the ACG Annual Scientific Meeting.
“The aims of our study were to study the association of withdrawal times and interval colorectal cancers, [and] to study the association of adenoma detection rate with interval cancers in the presence of withdrawal time,” Aasma Shaukat, MD, a gastroenterologist at the Minneapolis VA Medical Center, said in a presentation.
Shaukat and colleagues assessed 76,810 records of screening colonoscopies performed by 51 gastroenterologists in Minnesota from 2004 to 2009. They calculated average annual withdrawal times and adenoma detection rates and identified interval cancers using the linked state cancer registry.
The average annual withdrawal time was 8.6 minutes, and the average annual adenoma detection rate was 26%. During 249,261 person-years of follow-up, 56 interval cancers were identified, corresponding to an annual rate of 0.22/1,000 person-years. Withdrawal time was inversely associated with interval cancers (P<.0001), with withdrawal times <6 minutes corresponding to an adjusted incidence rate ratio (IRR) of 2.3 (95% CI, 1.5-3.4) compared with withdrawal times >6 minutes. Adenoma detection rate was not associated with interval cancer risk (P=.4), but longer withdrawal times were associated with higher adenoma detection rates (2.5% per minute; 95% CI, 1.5-3.5).
“Shorter average annual withdrawal times during screening colonoscopies are independently associated with an increased risk for interval colorectal cancer,” Shaukat concluded. “Longer withdrawal time is associated with higher adenoma detection rate, withdrawal times may be a more sensitive indicator of the risk of interval colorectal cancer than the adenoma detection rate in a practice that has high-quality colonoscopy, and future studies are needed to confirm this relationship.”
For more information:
Shaukat A. Abstract 25. Presented at: ACG Annual Scientific Meeting, Oct. 20-22, 2014; Philadelphia.
Disclosure: Relevant financial disclosures were not provided.
Perspective
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John J. Vargo, MD, MPH
Adenoma detection rate as well as withdrawal times are both important quality indicators of colonoscopy performance. We know from Kaminski et al. in the New England Journal of Medicine that adenoma detection rate will affect overall risk of colorectal mortality. We also know from data from Corley et al. from Kaiser Permanente that increasing adenoma detection rate confers decreasing colorectal cancer mortality. A robust adenoma detection rate is very much a lynchpin for decreasing colorectal cancer mortality.
This study is very interesting because it utilizes a group of 51 community-based gastroenterologists over a 5 year period encompassing over 76,000 colonoscopies. The authors were interested in the development of interval cancer. They found that the interval development of colorectal cancer was not related to the adenoma detection rate, but rather to the length of withdrawal time. More specifically, longer withdrawal times conferred a decreased risk of the interval development of colorectal cancer.
Why do we have this dichotomy? First and foremost, I think these quality outcomes for colonoscopy, both adenoma detection rate and withdrawal time, go hand in hand. Why did these authors see a difference in this study? Could it have been the preparation? I certainly feel that longer colonoscopy withdrawal time does equate with a higher quality colonoscopy, and again what we are seeing from emerging data is that optimizing adenoma detection rate is key for decreasing colorectal cancer mortality.
Shaukat et al. have demonstrated that that the interval for withdrawal time is again a key component in decreasing the interval development of colorectal cancer. Quality colonoscopy is an amalgam of experience, optimal preparation and maximizing both adenoma detection rate as well as withdrawal time. All are necessary to optimize polyp detection and therefore decrease any interval development of colorectal cancer.
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