A Rare Case of Bevacizumab and Radiation-Induced Ischemic Bowel Injury

Abstract

Ischemic colitis is a poorly documented side effect of the combination of palliative radiation and targeted therapy with Bevacizumab, a recombinant and humanized monoclonal antibody against the vascular endothelial growth factor receptor.1 We present a case of acute onset of ischemic colitis in a patient with prior pelvic irradiation undergoing treatment of metastatic rectal adenocarcinoma with Bevacizumab. A 68 y/o male with microsatellite stable, KRAS-mutated Stage IVB Rectal Adenocarcinoma status post 3 months of fluorouracil, oxaliplatin, folinic acid, abdominal perineal resection with ileo-colonic anastomosis with end colostomy, and palliative radiation to pelvis and spine presented with abdominal pain and bright red blood in his ostomy bag. Hemoglobin was 5.6 g/dL on admission, with appropriate response after transfusion. Recent endoscopy showed monlial esophagitis and non-bleeding erosive gastropathy. Colonoscopy 1 year prior showed multiple benign polyps. He underwent colonoscopy via colostomy, which was remarkable for both a continuous area of non-bleeding ulcerated mucosa and a segmental area of severely friable mucosa within the distal colon, neither with stigmata of recent bleeding. Histopathology demonstrated severely active colitis with ulceration. Colorectal surgery recommended no acute surgical intervention given his poor prognosis. Conventional therapy for treatment of metastatic colorectal cancer includes a fluoropyrimidine-based therapy with or without the use of targeted therapy and/or palliative radiation. Bevacizumab inhibits tumor neovascularization, which has proven beneficial when treating solid tumors by restricting tumor growth and metastatic ability.1 Radiation amplifies this effect by free radical formation, which promotes cell death. Results of a retrospective study looking at 33 patients undergoing therapy with Bevacizumab and prior radiation showed a 9% incidence of severe bowel complications, including acute ischemic colitis and bowel perforation.2 Ischemic colitis, a rare and minimally reported risk of therapy with Bevacizumab and radiation, should be considered in patients presenting with sudden onset of abdominal pain and hematochezia.1487_A Figure 1. Previously normal appearing descending colon1487_B Figure 2. Friability with absence of bleeding in distal colon1487_C Figure 3. Ulceration of distal colon