COLORECTAL CANCER RISK AFTER POLYP REMOVAL IN FECAL IMMUNOCHEMICAL TEST BASED COLORECTAL CANCER SCREENING

Background & Aims
Colonoscopy surveillance intervals are based on the predicted risk of metachronous colorectal cancer (CRC) after polyp removal. Due to the presence of co-existent findings at baseline colonoscopy, risk estimation per specific polyp subtype is difficult. To investigate the metachronous CRC risk, we evaluated the risk of patient groups with and without co-occuring findings.
Methods
Using screening colonoscopies performed after a positive fecal immunochemical test between 2014-2020 within the Dutch CRC screening program, we applied Cox regression analysis to evaluate the association between findings at baseline colonoscopy and metachronous CRC. Metachronous cancer cases, defined as CRCs diagnosed after 6 months of baseline colonoscopy, were collected from the Dutch Cancer Registry. Risk of subgroups based on polyp findings were compared to individuals without polyps in two different models. In model 1, individuals were classified into eight different subgroups based on the presence or absence of advanced adenomas and/or advanced serrated polyps. In model 2, we included presence of individual polyp characteristics in a multivariable analysis. Both models were adjusted for individuals’ sex and age. A hazard ratio >1.5 was considered clinically relevant. Advanced serrated polyps (ASP) were defined as serrated polyp ≥10mm, sessile serrated lesion with dysplasia, or traditional serrated adenoma.
Results
253,833 colonoscopies were included. Over a median follow-up of 36 months (IQR, 21-57), we identified 504 metachronous CRC cases. HR for CRC was 1.70 (CI95%, 1.07-2.69) for individuals with ASP without advanced adenomas (AA), 1.22 (0.96-1.55) for individuals with AAs without ASPs, and 2.00 (1.19-3.39) for individuals with ASPs and AA, compared to patients without polyps (Table 1). Individuals with non-advanced adenomas and/or non-advanced serrated polyps did not have an increased CRC risk. Model 2 showed that any villous adenoma (HR 2.732, 1.725-4.329), serrated polyp ≥10mm (HR 1.61; 1.06-2.45), sessile serrated lesion with dysplasia (HR 2.09; 1.12-3.88), traditional serrated adenoma (HR 2.668, 1.434-4.965), adenoma with high-grade dysplasia (HR 3.59; 2.17-5.94) and presence of at least five non-advanced adenomas (HR 2.13; 1.10-4.10) resulted in a clinically relevant increased risk for CRC, while any adenoma ≥10mm did not (HR 0.96; 0.74-1.25) (Table 2).
Conclusion
By evaluating high-quality screening colonoscopies with a median follow-up of 3 years and accounting for co-occuring findings, we observed an increased CRC risk in individuals that had ASPs with the presence of AAs, or individuals with ASPs without AAs. These findings could contribute to establish more restrictive post-polypectomy surveillance guidelines.