Gastrointestinal Cancer

SS 17 - GI 3 - Colon/Rectum/Anus

126 - A Matched Case-Control Analysis of Clinical Outcomes for Inflammatory Bowel Disease Patients With Rectal Cancer Treated With Pelvic Radiation Therapy

Monday, October 22
5:15 PM - 5:25 PM
Location: Room 214 C/D

A Matched Case-Control Analysis of Clinical Outcomes for Inflammatory Bowel Disease Patients With Rectal Cancer Treated With Pelvic Radiation Therapy
R. Mudgway1, A. K. Bryant2, C. O'Hare3, J. D. Murphy2, and D. R. Simpson3; 1University of California, Riverside, Riverside, CA, 2Department of Radiation Medicine, University of California, San Diego, La Jolla, CA, 3University of California, San Diego, La Jolla, CA

Purpose/Objective(s): The inflammation of the gastrointestinal tract seen in inflammatory bowel disease (IBD) may predispose patients to complications from radiation therapy. Prior studies addressing this topic have shown mixed results in terms of treatment-related toxicity. Furthermore, these studies have been limited in size and follow-up duration. The objective of this study is to examine the clinical outcomes including acute and late toxicity for IBD patients with rectal cancer treated with pelvic radiation and compare them to matched control patients without IBD.

Materials/Methods: Patients diagnosed with AJCC stage I-IV rectal cancer between 2000 and 2015 and treated with radiation therapy were identified from the Veterans Affairs Informatics and Computing Infrastructure (VINCI) database. The cohort included 142 rectal cancer patients with IBD (n = 71) and control patients without IBD (n = 71) matched by AJCC stage, year of diagnosis, and age. Outcomes included acute and late toxicity and cancer-specific mortality. Acute radiation toxicity rates were compared between groups in univariable logistic regression for unadjusted analyses and multivariable conditional logistic regression in adjusted analyses to account for matching. Long-term radiation toxicity and mortality outcomes were compared between groups with univariable Cox proportional hazards regression in unadjusted analyses and multivariable gamma frailty models in adjusted analyses.

Results: There were no differences between groups in the frequency of radiation treatment breaks (11.9% for IBD vs. 8.5% in non-IBD; p = 0.49) and need for anti-diarrheal medication during radiation (61.3% vs. 50.8%; p = 0.29). A trend toward higher risk of hospital admission during radiation therapy for IBD patients was noted (aOR 2.69, 95% CI 0.88-8.22, p = 0.08). At 5 years, IBD patients experienced a higher rate of small bowel obstruction (25.0% vs. 1.9%; p = 0.009) and a trend toward a higher rate of abdominopelvic adhesions were noted (17.6% vs. 6.8%; p = 0.05). Other long-term toxicity outcomes including chronic diarrhea, wound dehiscence, anorectal fistula, proctitis, anorectal stricture, and rectal perforation were similar across groups. Cancer-specific mortality was also similar between groups (adjusted hazard ratio [aHR] 0.73, 95% CI 0.35-1.52, p=0.40. Overall mortality was significantly lower in the IBD group (aHR 0.54, 95% CI 0.32-0.92, p=0.02) due to a lower rate of non-cancer mortality.

Conclusion: These results suggest that IBD patients with rectal cancer have similar oncologic outcomes to non-IBD patients and tolerate pelvic radiation with modest rates of acute toxicity. However, there does appear to be an increase in long-term risk of small bowel obstruction and abdominopelvic adhesions in patients with IBD.

Author Disclosure: R. Mudgway: None. A.K. Bryant: None. C. O'Hare: None. D.R. Simpson: None.

Ross Mudgway, BS

Disclosure:
No relationships to disclose.

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