Annual Scientific Meeting
Introduction: The serrated pathway may account for a significant proportion of colorectal cancer (CRC). Achieving adequate serrated polyp detection rates (SDR) may reduce the incidence of post colonoscopy CRC (PCCRC). We used data from the New Hampshire Colonoscopy Registry (NHCR) to determine if exams performed by endoscopists who have a clinically significant serrated polyp detection rate (CSSDR) of 7% or greater, proposed by Anderson/Butterly (GIE 2017), had a reduced incidence of PCCRC. In addition, we compared CSSDR to the adenoma detection rate (ADR), the currently used benchmark.
Methods: We defined PCCRC as any CRC diagnosed between 6 and 36 months after an exam with an adenoma on index and between 6 and 60 months following a normal exam. Exclusion criteria were any CRC diagnosed at index or within 3 months, incomplete exams, IBD, and genetic syndromes. Clinically significant serrated polyps (CSSP) were defined as any sessile serrated polyp, traditional serrated adenoma, serrated polyp >1 cm anywhere in the colon and any serrated polyp >5 mm proximal to the sigmoid. CSSDR was defined as number of screening exams with at least one CSSP divided by all screening exams. The exposure variable was a CSSDR of 7% and adenoma detection rate of 25%. Cox regression was used to model the risk of PCCRC in terms of the covariates at index exam. Covariates were age, BMI, smoking, index findings (large serrated polyp, advanced adenoma or any adenoma), followup time (months), bowel prep quality, having more than 1 surveillance exam and family history of CRC. We also compared receiver operating characteristics (ROC) for CSSDR 7% to an ADR 25% using probabilities derived from a logistic regression analysis.
Results: In our sample (142,950 index exams) 75 CRCs were diagnosed during the 6-60 month period (45 CRCs diagnosed between 6-36 months) after the index exam. The hazard ratio (HR) for CSSDR of 7% (HR=0.37 95% CI 0.17-0.83) was similar to that for an ADR of 25% (HR=0.45 95% 0.23-0.89) (Table 1). The ROCs were similar for CSSDR and ADR and the combination of the 2 rates did not alter the ROC (Table 2).
Discussion: Having an exam performed by an endoscopist with a CSSDR of 7% or greater was associated with a decrease incidence of PCCRC (HR=0.37). The performance of CSSDR and ADR for PCCRC incidence were similar. These data suggest that a CSSDR of 7% or greater may be associated with lower PCCRC rates. However, it may not add an information to that provided by the current primary colonoscopy benchmark, ADR.