The patient was a 68-year-old man who had an anal fistula for>10 years. He was referred to our institution after visiting a local physician with left femoral pain as the main complaint and received a diagnosis of high inflammatory response. We then found discharge of pus in the perianal region during a medical examination. We also found an extensive intrapelvic tumor during a computed tomography(CT)/magnetic resonance imaging examination. In addition, the level ofa tumor marker and inflammatory response were high. To control the inflammation, we performed seton drainage and sigmoid colostomy. On the basis of the pathological findings from the mucus component, we confirmed a diagnosis of fistula cancer. Considering that the progressive lesion had extensively spread, we decided to initiate chemotherapy alone because ofthe absence ofan indication for radiotherapy. We administered bevacizumab plus mFOLFOX6, and partial response was observed on a CT scan. We could control the progression ofthe disease for>6 months. The present case suggests that bevacizumab plus mFOLFOX6 can be an effective regimen for unresectable advanced fistula cancers.