2941 - Toxicity with Contemporary Radiotherapy in Inflammatory Bowel Disease Patients Treated for Pelvic Malignancies

J. ZInkin¹, Y. Ziemba², H. D. Zinkin³, M. Akerman⁴, and B. Parashar⁵; ¹Northwell Health, Lake Success, NY, ²Department of Pathology, Northwell Health, Lake Success, NY, ³Department of Radiation Medicine, Northwell Health, Lake Success, NY, ⁴Biostatistics Unit, Office of Academic Affairs, Northwell Health, Lake Success, NY, ⁵Northwell, Lake Success, NY

Purpose/Objective(s): Inflammatory bowel disease (IBD), which includes both Crohn’s (CD) and ulcerative colitis (UC) is characterized as an autoimmune disease of chronic bowel inflammation. Pelvic radiotherapy (RT) has traditionally been offered with discretion due to the concern of inducing severe enteritis and colitis. However, considering contemporary RT techniques such as intensity modulated radiation therapy (IMRT) and improved drugs for IBD, we performed a retrospective cohort study to review toxicities from RT for pelvic tumors in IBD patients. We hypothesized that patients with IBD do not experience increased RT toxicity. Materials/

Methods: Following IRB approval, we queried the patient database from 2010-2024 and identified 174 patients with a diagnosis of IBD and rectal or uterine cancer. Following exclusions (i.e. missing data, no IBD diagnosis, treatment with surgery alone), 22 patients were analyzed who met the inclusion criteria. Variables collected included type of RT (pelvic v brachytherapy), fractionation (hypofractionation v conventional), toxicity (CTCAE v.5 grading), type of systemic treatment [Chemotherapy (C) or Immunotherapy (IO)], and IBD medications during therapy. Descriptive statistics were calculated for the overall sample, as well as by toxicity grade group (0-1 vs. 2-3). The two toxicity groups were compared using the Fisher’s exact test for categorical variables and the Wilcoxon rank sum test (the non-parametric counterpart to the two-sample t-test) for continuous data.
Results: Amongst the 22 patients treated, 77.28% (n=17) experienced CTCAE grades 0-1 gastrointestinal toxicity, 18.18% (n=4) grade 2 and 4.55% (n=1) grade 3 toxicity. No variables significantly impacted toxicity including gender (p=0.135), diagnosis (UC vs CD) (p=0.613), type of cancer (rectal v uterine) (p=0.266), dose fractionation (p=0.111), total RT dose (p=0.289), RT technique (IMRT vs 3DCRT) (n=0.589), duration of IO or C (p=1.000) or IBD medication use during treatment (p=1.000). Only one patient did not complete the prescribed course of RT due to grade 3 diarrhea. This was a male with UC and rectal cancer prescribed 5040 cGy with a 3DCRT plan. A diagnosis of IBD affected the physician’s treatment plan in 36.4% of patients, yet all received RT. These included decisions to offer adjuvant vaginal brachytherapy to minimize the risk of requiring EBRT in the future, hold immunotherapy, and sequence chemotherapy prior to pelvic RT.
Conclusion: Patients with IBD may not require modification of standard of care radiotherapy protocols for uterine and rectal cancer. Prospective studies are warranted to further clarify the role of modern techniques such as IMRT and adaptive therapy, as well as novel treatments such as immunotherapy in the management of IBD patients with malignancies. It is vital that these patients are not offered substandard therapies without supporting data.