Radiation Therapy for Cancer Patients With Inflammatory Bowel Disease: A Systematic Review

Background: Inflammatory bowel disease (IBD) has been historically considered a relative contraindication to the use of radiation therapy (RT) due to the risk of disease exacerbation and gastrointestinal toxicity. Currently, there are no established guidelines for the use of RT in patients with IBD, and there is limited available data on how well patients with IBD can tolerate RT. The objective of this systematic review is to assess the literature regarding the use of RT in the treatment of abdominal and/or pelvic cancer in patients with IBD. Methods: An electronic search was conducted on PubMed, Cochrane, Embase, and Medline. Eligible studies consisted of all peer-reviewed articles published in English that reported outcomes of RT use in the treatment of abdominal or pelvic neoplasms in patients with IBD. Review articles and case reports were excluded. We evaluate all the evidence on RT outcomes, namely GI toxicity and IBD activity. Results: A total of 18 articles with 1,109 patients were identified and included in this systematic review. The included studies were published between 1998 and 2021. The majority had a retrospective study design (14/18, 77%). Patients were most commonly treated for prostate cancer (11/18 studies; 61%), followed by colorectal cancer (4/18 studies; 22%), or any pelvic cancer (3/18; 16%). External beam radiation therapy was evaluated in 10 studies (55%), brachytherapy in 6 studies (33%), and stereotactic RT in 2 studies (11%). IBD activity following RT was assessed in 5 studies. IBD flares within 6 months of RT administration ranged between 3.5% and 15%. Identified risk factors for flares were the presence of IBD involving the rectum and the concomitant use of chemotherapy with RT. GI toxicities post-RT were reported in 16/18 studies (88%). Diarrhea and proctitis were the most commonly encountered low-grade toxicities, with incidences of up to 32% for diarrhea and 27% for proctitis. Rectal bleeding ranged from 5% to 23%. Acute grade III-IV GI toxicities ranged between 5% and 23% among the studies, while late grade III-IV GI toxicities ranged between 5% and 15%. IBD patients receiving RT had significantly higher rates of wound dehiscence and small bowel obstruction when compared to patients without IBD. When comparing different types of RT, one study confirmed that intensity-modulated radiotherapy had significantly lower rates of grade ≥ 2 toxicities when compared to three-dimensional conformal RT. Conclusions: RT for cancer treatment in patients with IBD appears to be associated with acceptable rates of high-grade GI toxicities. The judicious use of RT in IBD must be emphasized, with factors such as IBD location and baseline disease activity requiring consideration. More importantly, the oncological benefits and possible detrimental effects on IBD should always be balanced. Future prospective studies are needed to further investigate disease flares and toxicities, assess the risks and benefits associated with different subtypes of RT, and explore RT parameters such as radiation dose and technique.