Risk of colorectal cancer incidence and mortality after removals of polyps: a cohort study using the UK Biobank

Colorectal cancer (CRC) is a leading cause of cancer death worldwide, however, the risk of newly-diagnosed CRC and its related mortality after polypectomy have not been conclusively determined.

Prospective cases with polypectomy were identified in the UK Biobank. The age- and sex-standardized incidence ratio (SIR) and standardized mortality ratio (SMR) were calculated to assess the risk of CRC between the removal group and both the non-index-colonoscopy group (no record of diagnostic colonoscopy) from the UK Biobank and the general population in England. We also estimated the effect of removal compared with the polyp-free group using a competing risk model.

During a median follow up of 10 (1-44) years (51,136 person-years), 78 incident CRCs (153/100,000 person-years), and 16 CRC-specific deaths (31/100,000 person-years) were identified in the removal group. Compared with the general population in England, the removal group had a similar risk of incident CRC (SIR 0.81, 95% confidence interval [CI] 0.64-1.01; P=0.060), whereas the CRC-specific mortality was 52% lower (SMR 0.48, 95%CI 0.28-0.78; P=0.004). Compared with the non-index-colonoscopy group, CRC-specific deaths after polyp removal were not significantly different (SMR 1.64, 95%CI 0.94-2.66; P=0.050). Compared with the polyp-free group, the risks of incidence and mortality in the removal group were both greater (incidence: adjusted hazard ratio [HR] 6.17, 95%CI 4.36-8.74; P<0.001; mortality: adjusted HR 3.25, 95%CI 1.65-6.41; P<0.001).

Polypectomy reduced but not eliminated the risk of CRC for polyp-positive participants to the level of the general population, reinforcing the importance of procedural quality and tailored surveillance strategies.