Colorectal cancer risk following polypectomy in a multicentre, retrospective, cohort study: an evaluation of the 2020 UK post-polypectomy surveillance guidelines

Abstract

Objective: Colonoscopy surveillance aims to reduce colorectal cancer (CRC) incidence after polypectomy. The 2020 UK guidelines recommend surveillance at 3 years for 'high-risk' patients with ≥2 premalignant polyps (PMPs), of which ≥1 is 'advanced' (serrated polyp (or adenoma) ≥10 mm or with (high-grade) dysplasia); ≥5 PMPs; or ≥1 non-pedunculated polyp ≥20 mm; 'low-risk' patients without these findings are instead encouraged to participate in population-based CRC screening. We examined the appropriateness of these risk classification criteria and recommendations.

Design: Retrospective analysis of patients who underwent colonoscopy and polypectomy mostly between 2000 and 2010 at 17 UK hospitals, followed-up through 2017. We examined CRC incidence by baseline characteristics, risk group and number of surveillance visits using Cox regression, and compared incidence with that in the general population using standardised incidence ratios (SIRs).

Results: Among 21 318 patients, 368 CRCs occurred during follow-up (median: 10.1 years). Baseline CRC risk factors included age ≥55 years, ≥2 PMPs, adenomas with tubulovillous/villous/unknown histology or high-grade dysplasia, proximal polyps and a baseline visit spanning 2-90 days. Compared with the general population, CRC incidence without surveillance was higher among those with adenomas with high-grade dysplasia (SIR 1.74, 95% CI 1.21 to 2.42) or ≥2 PMPs, of which ≥1 was advanced (1.39, 1.09 to 1.75). For low-risk (71%) and high-risk (29%) patients, SIRs without surveillance were 0.75 (95% CI 0.63 to 0.88) and 1.30 (1.03 to 1.62), respectively; for high-risk patients after first surveillance, the SIR was 1.22 (0.91 to 1.60).

Conclusion: These guidelines accurately classify post-polypectomy patients into those at high risk, for whom one surveillance colonoscopy appears appropriate, and those at low risk who can be managed by non-invasive screening.

Keywords: colonoscopy; colorectal adenomas; colorectal cancer; colorectal cancer screening; surveillance.

Figure 1

Study profile flow diagram. ^aNot mutually exclusive. ^bReasons for lost to follow-up included having all examinations after emigrating (n=20); having no surveillance and being untraceable through national data sources (n=22); and having an unknown date of birth (n=4). ^cHigh-risk patients were those with ≥2 premalignant polyps, of which ≥1 was advanced, ≥5 premalignant polyps or ≥1 large (≥20 mm) non-pedunculated premalignant polyp; low-risk patients had none of these findings. CRC, colorectal cancer.

Figure 2

Cumulative incidence of colorectal cancer by time from baseline, first surveillance and second surveillance. Cumulative incidence of colorectal cancer without surveillance (censoring at any first surveillance visit) for the whole cohort (A) and for low-risk and high-risk patients (B). Cumulative incidence of colorectal cancer after first surveillance (censoring at any second surveillance visit) for the whole cohort (C) and for low-risk and high-risk patients (D). Cumulative incidence of colorectal cancer after second surveillance (censoring at end of follow-up) for the whole cohort (E) and for low-risk and high-risk patients (F). 95% CIs are shown for each curve. High-risk patients were those with ≥2 premalignant polyps, of which ≥1 was advanced, ≥5 premalignant polyps or ≥1 large (≥20 mm) non-pedunculated premalignant polyp; low-risk patients had none of these findings.