WB: IBD Plus Colectomy Increases Rectal Cancer Risk Up to 10-Fold

Patients with IBD and subtotal colectomy experienced a higher risk for rectal cancer compared with those with IBD and no colectomy and a background population.

“It is well-known that long-standing colorectal inflammation, as seen in some cases of IBD, may lead to increased risk for colorectal cancer,” Tine Jess, MD, DMSc, notes. “This has led to surveillance guidelines on how to optimally follow patients with long-standing, extensive IBD. However, these guidelines rarely cover patients who have had their colon removed by subtotal colectomy, even though cancer could still develop in their rectum.”

A limited body of literature provides support for rectal cancer surveillance following colectomy in patients with IBD, but those findings “cannot stand alone,” according to Dr. Jess and colleagues in a study published in Gastro Hep Advances. Dr. Jess and colleagues conducted a population-based cohort study to assess the risk for rectal cancer following subtotal colectomy in patients with IBD. Among patients with IBD, 4,931 had a colectomy. The researchers followed patients in that group, which included 1,248 with Crohn’s disease and 3,683 with ulcerative colitis, for 31,243 person-years and compared the results with 49,203 patients with IBD (CD, 12,397; UC, 36,806) who had not undergone colectomy (follow-up, 620,808 person-years).

Rectal Cancer Rates Highest With IBD & Colectomy

Age at the time of IBD onset was higher in the UC subgroup (mean, 38.51 years) compared with the CD group (mean, 34.39 years), while age at the time of subtotal colectomy was slightly higher in the UC group (mean, 42.43 years) compared with the CD group (mean, 38.97 years). There were more women (60.7%) than men (39.3%) in the CD subgroup; rates were comparable in the UC subgroup.

The researchers identified 42 cases of rectal cancer among 4,931 patients (0.9%) after subtotal colectomy with a diverted rectum versus 209 cases among 49,251 patients in the matched IBD cohort without colectomy (0.4%) and 941 cases among 246,550 participants in the background population (0.4%).

Compared with patients without colectomy, Dr. Jess and colleagues reported HRs for rectal cancer in patients with IBD and a diverted rectum of 0.76 (95% CI, 0.28-2.07) within 10 years of colectomy and 7.56 (95% CI, 5.21-10.86) 10 years after colectomy. The HR for patients with a diverted rectum was 0.84 (95% CI, 0.31-2.24) compared with 10.01 (95% CI, 7.20-13.94) for the background population.

Rectal Cancer Risk 10 Years After Surgery

“Our findings indicating an 8- to 10-fold increased risk for cancer 10 years after surgery, when compared with both a matched IBD cohort without surgery and with the general population, calls for better long-term surveillance after surgery and for better guidelines,” Dr. Jess says.

She also notes that this increased risk for rectal cancer following surgery “only becomes evident after 10 years, and it affects both women and men and both patients with CD and UC” (Table).

The results indicate the need for improved surveillance as well as better guidelines, she continues. “Further research into the magnitude of risk and pathophysiology is also required, but this may be challenging because of a limited number of cohorts worldwide that are large enough to be statistically powered to investigate this,” Dr. Jess says. “For now, clinicians will have to act based on the existing evidence.”