A 65-year-old man with urination difficulty visited our hospital. Because his prostate-specific antigen level was 1,619 ng/ml, we performed a prostate biopsy. The biopsy specimen yielded a diagnosis of adenocarcinoma with a Gleason score of 4＋4. Computed tomography and bone scintigraphy showed lymph node, lung, and bone metastasis (cT3bN1M1). After 13 months of combined androgen blockade, he underwent treatment with a bisphosphonate. At 22 months of treatment, he developed bisphosphonate-related osteonecrosis of the jaw, and all necrotic bone and teeth were removed. He subsequently underwent repeated cleaning and fixation (splinting) for an oral fistula and mandibular fracture. Emergency transcatheter arterial embolization was then performed to treat a bleeding of the facial artery aneurysm. An oral infection and aspiration pneumonia repeatedly developed secondary to the oral fistula. The patient underwent a gastrostomy, after which his nutritional status improved and he was discharged.