Colorectal cancer risk following adenoma removal: a large prospective population-based cohort study

Background: Randomised controlled trials have demonstrated significant reductions in colorectal cancer (CRC) incidence and mortality associated with polypectomy. However, little is known about whether polypectomy is effective at reducing CRC risk in routine clinical practice. The aim of this investigation was to quantify CRC risk following polypectomy in a large prospective population-based cohort study. <br/><br/>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 up to 31st December 2010. CRC standardised incidence ratios (SIRs) were calculated and Cox proportional hazards modelling applied to determine CRC risk. <br/><br/>Results: During 44,724 person-years of follow-up, 193 CRC cases were diagnosed amongst 6,972 adenoma patients, representing an annual progression rate of 0.43%. CRC risk was significantly elevated in patients who had an adenoma removed (SIR 2.85; 95% CI: 2.61 to 3.25) compared with the general population. Male sex, older age, rectal site and villous architecture were associated with an increased CRC risk in adenoma patients. Further analysis suggested that not having a full colonoscopy performed at, or following, incident polypectomy contributed to the excess CRC risk. <br/><br/>Conclusions: CRC risk was elevated in individuals following polypectomy for adenoma, outside of screening programmes. <br/><br/>Impact: This finding emphasises the need for full colonoscopy and adenoma clearance, and appropriate surveillance, after endoscopic diagnosis of adenoma.