Purpose: Inflammatory bowel disease (IBD) is a known risk factor for rectal cancer, and RT is often an important part of therapy for these patients. Previously published studies have raised concerns for increased rates of RT toxicity in patients with IBD. We performed a matched case-control analysis to assess RT-related toxicity in a large sample of U.S. veterans afflicted with IBD and rectal cancer.
Methods and materials: We identified 186 veterans with rectal cancer (71 Patients with IBD treated with RT, 71 matched controls without IBD treated with RT, and 44 nonmatched controls with IBD treated without RT) diagnosed between 2000 and 2015. We analyzed short- and long-term toxicity and mortality in multivariable logistic regression, Fine-Gray, and frailty models, adjusting for potential confounders.
Results: When comparing patients with and without IBD treated with RT there were no differences in RT breaks (adjusted odds ratio [aOR], 1.70; 95% confidence interval [CI], 0.38-4.76; P = .49) or the need for antidiarrheal medication during RT (aOR, 1.53; 95% CI, 0.70-3.35; P = .29). There was a trend toward higher risk of hospital admission during RT for RT + patients with IBD (aOR, 2.69; 95% CI, 0.88-8.22; P = .08). There were higher rates of small bowel obstruction (OR, 15; 95% CI, 1.9-115; P = .009) and a trend toward higher rates of abdominopelvic adhesions (OR, 3.6; 95% CI, 0.98-13; P = .05) in the RT + IBD cohort. However, compared with a nonmatched cohort of patients with IBD treated without RT there were no differences in long-term complications. No differences were found in other acute or long-term toxicities. Rectal cancer-specific mortality appeared similar across all cohorts.
Conclusions: RT does not appear to increase the rates of acute or long-term toxicity in patients with IBD and should be considered a standard part of therapy when otherwise indicated.
Copyright © 2019 Elsevier Inc. All rights reserved.