Risk of Rectal Cancer After Colectomy for Patients With Ulcerative Colitis: A National Cohort Study.

Background & Aims: Patients with ulcerative colitis (UC) have an increased risk of rectal cancer, therefore reconstruction with an ileal pouch-anal anastomosis (IPAA) generally is preferred to an ileorectal anastomosis (IRA) after subtotal colectomy. Similarly, completion proctectomy is recommended for patients with ileostomy and a diverted rectum, although this approach has been questioned because anti-inflammatory agents might reduce cancer risk. We performed a national cohort study in Sweden to assess the risk of rectal cancer in patients with UC who have an IRA, IPAA, or diverted rectum after subtotal colectomy.

Methods: We collected data from the Swedish National Patient Register for a cohort of 5886 patients with UC who underwent subtotal colectomy with an IRA, IPAA, or diverted rectum from 1964 through 2010. Patients who developed rectal cancer were identified from the Swedish National Cancer Register. The risk of rectal cancer was compared between this cohort and the general population by standardized incidence ratio analysis.

Results: Rectal cancer occurred in 20 of 1112 patients (1.8%) who received IRA, 1 of 1796 patients (0.06%) who received an IPAA, and 25 of 4358 patients (0.6%) with a diverted rectum. Standardized incidence ratios for rectal cancer were 8.7 in patients with an IRA, 0.4 in patients with an IPAA, and 3.8 in patients with a diverted rectum. Risk factors for rectal cancer were primary sclerosing cholangitis in patients with an IRA (hazard ratio, 6.12), and colonic severe dysplasia or cancer before subtotal colectomy in patients with a diverted rectum (hazard ratio, 3.67).

Conclusions: In an analysis of the Swedish National Patient Register, we found that the risk for rectal cancer after colectomy in patients with UC is low, in relative and absolute terms, after reconstruction with an IPAA. An IRA and diverted rectum are associated with an increased risk of rectal cancer, compared with the general population, but the absolute risk is low. Patients and their health care providers should consider these findings in making decisions to leave the rectum intact, perform completion proctectomy, or reconstruct the colon with an IRA or IPAA.