Impact of abdominal or pelvic radiotherapy on disease activity in inflammatory bowel disease: a multicentre cohort study from the GETAID.

Abdominal or pelvic radiotherapy in inflammatory bowel disease (IBD) patients raises concerns regarding the risk of worsening of underlying disease. To assess the impact of radiotherapy on IBD course. A retrospective multicentre study including IBD patients exposed to abdominal or pelvic irradiation was conducted, retrieving IBD activity by semester (6-month periods) before (from S-4 to S-1) and after (from S + 1 to S + 6) radiotherapy and IBD flare during follow-up. Sixty-one patients (32 women, mean age 59 years), with 467 patient semesters of follow-up, treated for digestive (n = 31), urinary tract (n = 23) and gynaecological cancers (n = 7) were included. Rates of IBD activity per semester were, respectively, 21% (95% CI: 16-27) from S-4 to S-1; 12% (7-19) from S + 1 to S + 3 (P = 0.15 vs S-4 to S-1) and 16% (10-25) from S + 4 to S + 6 (P = 0.45 vs S-4 to S-1). With a median follow-up of 156 weeks (interquartile range: 82-365), rates of survival without IBD flare at 1 and 3 years after radiotherapy were 82.5% (73.2-93.0) and 70.6% (58.8-84.7). Moderate-to-severe acute radiotherapy-induced gut toxicity and the absence of concomitant chemotherapy were independently associated with an increased risk of flare. Most patients with non-active IBD can be safely treated with abdominal or pelvic radiotherapy. Patients having acute gut toxicity and those without concomitant chemotherapy should be more closely monitored in the post-radiotherapy period.