A case report of rectal perforation associated with bevacizumab treatment after carbon ion radiotherapy for recurrent rectal cancer

Bevacizumab, an antibody that targets vascular endothelial growth factor, is commonly used in the treatment of unresectable or recurrent colorectal cancer in combination with 5-fluorouracil-based chemotherapy. Clinical studies have shown, however, that bevacizumab administration can give rise to a number of adverse events including hypertension, proteinuria, bleeding, gastrointestinal perforation, thrombosis, and wound-healing complications. Among these, potentially fatal gastrointestinal perforations occur in 1-3 % of patients. A possible risk factor for this particular adverse event is a recent history of abdominal/pelvic irradiation. Carbon ion radiotherapy for recurrent rectal cancer is safer and results in better local control than conventional radiotherapy. This might be an even more effective option if followed by 5-fluorouracilbased chemotherapy and bevacizumab administration, although this is yet to be definitively demonstrated. Here, we report a case of rectal perforation in a patient treated with bevacizumab subsequent to carbon ion beam therapy for recurrent rectal cancer. Histological evaluation of bowel biopsies revealed inflammation similar to that associated with X-ray irradiation. In conclusion, just as with conventional abdominal/pelvic irradiation, it is important to consider the possibility of gastrointestinal perforation during bevacizumab treatment following carbon ion beam therapy.