Incidence of rectal cancer after colectomy for inflammatory bowel disease: nationwide study.

Background: Inflammatory bowel disease increases the risk of colorectal neoplasia. A particular problem arises in patients who have undergone subtotal colectomy leaving a rectal remnant. The risk of future rectal cancer must be accurately estimated and weighed against the risks of further surgery or surveillance. The aim of this study was to estimate the 10-year cumulative incidence of rectal cancer in such patients.

Methods: A nationwide study using England's hospital administrative data was performed. A cohort of patients undergoing subtotal colectomy between April 2002 and March 2014 was identified. A competing risks survival analysis was performed to calculate the cumulative incidence of rectal cancer. The effect of the COVID-19 pandemic on endoscopic surveillance was investigated using time-trend analysis.

Results: A total of 8120 patients were included and 61 patients (0.8%) were diagnosed with cancer. The cumulative incidence of rectal cancer was 0.26% (95% c.i. 0.17% to 0.39%), 0.49% (95% c.i. 0.36% to 0.68%), and 0.77% (95% c.i. 0.57% to 1.02%) at 5, 10, and 15 years respectively. A previous diagnosis of colonic dysplasia (HR 3.34, 95% c.i. 1.01 to 10.97; P = 0.047), primary sclerosing cholangitis (HR 5.42, 95% c.i. 1.34 to 21.85; P = 0.018), and elective colectomy (HR 1.83, 95% c.i. 1.11 to 3.02; P = 0.018) was associated with an increased incidence of rectal cancer. Regarding endoscopic surveillance, there was a 43% decline in endoscopic procedures performed in 2020 (333 procedures) compared with 2019 (585 procedures).

Conclusion: The incidence of rectal cancer after subtotal colectomy is low. Asymptomatic patients without evidence of rectal dysplasia should be carefully counselled on the possible benefits and risks of prophylactic proctectomy.