The number of adenomas per colonoscopy (APC) is inversely correlated with postcolonoscopy colorectal cancer (PCCRC), which supports use of APC as a new quality control measure, according to investigators.
Dr. Joseph C. Anderson
Data from 138 endoscopists showed that patients screened by physicians with higher APCs had significantly lower rates of PCCRC, and an APC of 0.6 offered more protection than either an APC of 0.4 or an adenoma detection rate (ADR) of 25%, reported lead author Joseph C. Anderson, MD, of White River Junction VA Medical Center, Hanover, N.H., and colleagues.
“Unfortunately, APC has never been validated as a quality measure by demonstrating a reduction in PCCRC in exams performed by endoscopists with higher rates,” Dr. Anderson said at the annual meeting of the American College of Gastroenterology.
To this end, Dr. Anderson and colleagues reviewed data from the New Hampshire Colonoscopy Registry (NHCR), including 9,023 screening colonoscopies with a follow-up event 6-60 months after the initial exam. Procedures were conducted by 138 endoscopists in New Hampshire, Vermont, Massachusetts, and Maine.
Three quality measures were analyzed for associations with PCCRC: an APC of 0.4, an APC of 0.6, and an ADR of 25%. Hazard ratios were calculated for all PCCRCs, as well as PCCRCs diagnosed at first follow-up event. Rates were reported for two time periods: 6-36 months and 6-60 months.
From 6 to 60 months, 82 cases of PCCRC were diagnosed, among which 50 were diagnosed between 6 and 36 months.
For both periods, all three quality measures were significantly associated with reductions in PCCRC. The higher APC of 0.6, however, offered greater protection, reducing all PCCRCs by 71% and 61% in the shorter and longer period, respectively. In comparison, the lower APC of 0.4 reduced rates by 63% and 53%, while the ADR benchmark reduced rates by 62% and 42%.
These trends were maintained for PCCRCs diagnosed at first follow-up event. An APC of 0.6 was associated with respective reductions of 79% and 65% for the shorter and longer period, compared with 64% and 57% for the lower APC, and 67% and 49% for ADR.
Additional analysis clarified the relationship between APC level and likelihood of developing PCCRC. In terms of absolute risk, patients screened by an endoscopist with an APC greater than 0.6 had a 0.5% chance of developing PCCRC from 6 to 36 months, compared with 0.7% for an APC of 0.4-0.6, and 2.1% for an APC of less than 0.4 (P = .0001). This pattern held through 60 months, during which time an APC greater than 0.6 was associated with an absolute risk of PCCRC of 0.4%, compared with 0.7% for an APC of 0.4-0.6, and 1.6% for an APC less than 0.4 (P = .0001).
“Our novel data support the use of APC as a quality measure by demonstrating a reduction in PCCRC risk in exams performed by endoscopists with higher APCs,” Dr. Anderson concluded, noting that an APC of 0.6 appeared to offer more protection than an APC of 0.4. “I feel that ... APC as a quality measure, now that we’ve validated it, may be accepted because of its ability to differentiate endoscopists on their adenoma detection skills.”
According to Lawrence Hookey, MD, of Queen’s University, Kingston, Ont., “It’s an important study that will probably contribute to where we’re going forward.”
Dr. Lawrence, chair of the division and medical director of the endoscopy units at Kingston General and Hotel Dieu hospitals, said that APC may overcome the main concern with ADR – that endoscopists who find one adenoma may not be motivated to seek out as many as possible.
“The problem with ADR, in general, is that if you find one polyp, and if ADR is the stat you’re living by, then you don’t need to find any other polyps, and that obviously doesn’t do that patient a favor, necessarily,” Dr. Hookey said in an interview. “It does bring them back sooner for surveillance, but it doesn’t help remove the rest of the polyps that they have. And not that someone is going to find one polyp and turn off the light and pull the scope out, but you may not be looking as hard.”
APC mitigates this issue, he explained, because it determines “whether or not you’re truly clearing things out and getting rid of as many [polyps] as possible.”
Dr. Hookey said that APC is “probably the best” quality control measure on the horizon, and he suggested that more work is needed to determine the optimal benchmark figure, which should ideally be investigated through larger studies.
“I just want to see it in bigger groups,” he said.
The investigators and Dr. Hookey reported no conflicts of interest.