Increased risk of ischemic bowel complications during treatment with bevacizumab after pelvic irradiation: report of three cases.

Purpose: To assess the rate of severe bowel complications during treatment with the anti-vascular endothelial growth factor monoclonal antibody bevacizumab.
Methods and Materials: We performed a retrospective evaluation of bevacizumab-associated severe intestinal adverse events from our institutional database.
Results: A total of 33 patients started treatment with bevacizumab at our institution during the first 6 months after its approval in Germany. Three patients (9%) presented with severe bowel complications: two with acute ischemic colitis and one with gastrointestinal perforation with a fatal outcome. All 3 patients had undergone radiotherapy directed to the pelvis before treatment with bevacizumab. None of the 30 patients without bowel complications had been pretreated with infradiaphragmatic irradiation. Histologic evaluation of bowel biopsies and resection specimens revealed severe ischemic bowel damage as the pathophysiologic background of the clinical findings.
Conclusion: This report contributes to the pathophysiologic clarification of bevacizumab-induced bowel complications and points to a potentially increased risk of severe ischemic damage during treatment with bevacizumab in patients who have undergone previous radiotherapy.