Abstract
Bevacizumab (BV)-containing chemotherapy has led to a significant therapeutic effect in metastatic colorectal cancer treatment, however, it is associated with serious adverse events ; the incidence of fistula formation has been reported to be 0.33%. We report three patients who developed the fistula formation during BV-containing chemotherapy. One patient had ascending colon cancer with liver metastases, two patients had rectal cancer with pulmonary metastases and all patients underwent resection of the primary tumor. All patients developed anal fistula, and one patient was complicated by a rectovaginal fistula as well. Fistula formation occurred from 4 weeks to 10 months after the initiation of BV regimen and the number of doses of BV injection ranged from 2 to 17 times ; there was no consistent tendency. All patients complained of diarrhea caused by postoperative dyschezia or the chemotherapy. It is etiologically considered that, in the antecedent mucosal injury of the rectal anal region, BV-relating impaired neovascularization and delayed wound healing were added to cause these events. One patient showed progression of the disease caused by interruption of chemotherapy, two required colostomy for healing. We should note possible occurrence of fistula formation during BV-containing chemotherapy because the fistula formation might reduce QOL of the patients and affect the prognosis.
