EFFECT OF PELVIC RADIATION ON ILEAL POUCH OUTCOMES IN PATIENTS WITH INFLAMMATORY BOWEL DISEASE

Abstract INTRODUCTION Pouch creation surgery is a surgical treatment for patients with inflammatory bowel disease (IBD). Subsequent radiation therapy can affect the structural integrity and function of an ileal pouch. We aimed to determine the impact of pelvic radiation on pouch outcomes in patients with IBD. METHODS In this multicenter retrospective chart review, patients with IBD and pouch creation surgery who received pelvic radiation therapy between 2010-2024 were identified. Pouch complications of interest included worsening pelvic symptoms, pouchitis, development of a fistula or stricture, and pouch failure (excision/diversion) during or after radiation therapy. The Pouchitis Disease Activity Index (PDAI) was calculated before and after radiation to assess the severity of pouchitis based on symptoms (S-PDAI), endoscopy (E-PDAI), and pathology (P-PDAI). RESULTS Of 16 patients with IBD and an ileal pouch included in the study, 12, 3 and 1 patients had ulcerative colitis (UC), Crohn’s disease (CD), and indeterminate colitis, respectively. Mean duration from pouch surgery to radiation was 13.9 years. Mean cumulative radiation dose was 41.8 Gy. Indications for pelvic radiation therapy (number of patients) were prostate cancer (7), endometrial and ovarian cancer (3), bladder cancer (2), lymphoma (2), anorectal cancer (1), and pouch cancer (1). Pouch complications occurred in 10 patients (62.5%). Three (19%) patients had pouch failure at a mean of 8.2 months after radiation therapy. Pouchitis occurred in 8 (50%) patients, stricture in 4 (25%) patients, and fistula in 2 (12.5%) patients. None of the patients with CD developed a complication following radiation, compared to 90% of patients with UC (p = 0.04) (Table 1). Pouch age, type of pouch, duration of IBD diagnosis, and cumulative radiation dose were not associated with a pouch complication. The total PDAI increased significantly post radiation with mean difference (MD) of 3.7 (range, 5.4 to 9.1) (p = 0.001). All PDAI components increased significantly after radiation: SPDAI (1.9), EPDAI (1.3), and PPDAI (0.7) (Figure 1). The cumulative radiation dose was not correlated with the PDAI change (correlation coefficient of -0.49, p = 0.86). CONCLUSION In our small cohort of IBD patients, pelvic radiation therapy resulted in pouch complications in a significant number with a history of UC but not CD, including pouch failure and a significant increase in PDAI. These findings underscore the role of preoperative counselling and postoperative management in patients undergoing pelvic radiation. Further study on a larger number of patients is needed to determine if radiation as part of cancer treatment is reasonable and ways to mitigate pouch injury if radiation necessary.