Colorectal cancer risk in patients following polyp removal: a large prospective population-based cohort study

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Aims

Colorectal cancer (CRC) typically originates from colorectal polyps. Colorectal polyps are broadly categorised as either adenomas (dysplastic polyps which can progress via the page 10 adenoma-carcinoma sequence) or hyperplastic polyps (which, aside from rare serrated polyps, are usually benign). The aim of this investigation was to quantify CRC risk following polypectomy in a large population-based study

Methods

Patients with incident colorectal polyps between 2000 and 2005 in Northern Ireland (NI) were identified via electronic pathology reports received to the NI Cancer Registry (NICR). Patients were matched to the NICR to detect CRC and deaths, respectively, up to 31st December 2010. CRC standardised incidence rates (SIRs) were calculated and Cox proportional hazards modelling applied to determine CRC risk.

Results

During 73,474 person-years of follow-up, 234 CRC cases were diagnosed amongst 6,972 adenoma and 3,464 hyperplastic polyp patients without a concurrent adenoma, representing annual progression rates of 0.43% and 0.17%, respectively. CRC risk was significantly elevated in both adenoma (SIR 285; 95% CI: 261-325) and hyperplastic polyp (SIR 179; 95% CI: 134-214) patients compared with the general population. In adenoma patients, being male, having rectal or villous adenomas were associated with an increased CRC risk. Older age increased CRC risk in all polyp patients. Further analysis suggested that not having a full colonoscopy performed at, or following, incident polypectomy contributed to the excess CRC risk.

Conclusion

CRC risk remained elevated in individuals following polypectomy for adenomas or hyperplastic polyps, outside of screening programmes. These findings have significant implications for colorectal polyp surveillance guidelines.