A patient with a pancreatic neuroendocrine tumor and multiple liver metastases achieved a long-term partial response to third-line streptozocin treatment.

Abstract

The Japanese guideline for gastroenteropancreatic neuroendocrine tumor treatment recommends everolimus or sunitinib as first-line treatment for unresectable pancreatic neuroendocrine tumors (PNETs). Streptozocin (STZ) is recommended as an alternative. We encountered a patient with PNET who had multiple liver metastases and who showed a remarkable response to third-line STZ. The patient was a 50-year-old man with a pancreatic head tumor 32mm in diameter. We planned to perform subtotal stomach-preserving pancreaticoduodenectomy, but abandoned resecting the pancreas during the surgery upon discovering a small liver tumor 3mm in diameter, examination of frozen sections of which revealed a poorly differentiated adenocarcinoma. However, the final pathological examination revealed that the liver nodule was a PNET; hence, we completed the subtotal stomach-preserving pancreaticoduodenectomy 5weeks after the first laparotomy. The patient received no adjuvant chemotherapy after surgery. Twenty-one months later, we discovered 20 scattered liver metastases via computed tomography; these were considered unresectable. Therefore, we administered everolimus for 7months, but the patient developed interstitial pneumonia and experienced metastatic progression. Subsequent sunitinib administration for 6months was ineffective. Finally, we chose STZ (1000mg/m2, weekly) as a third-line treatment, which produced a partial response for 10months. The patient remains alive 38months after the detection of recurrence. As the order in which anti-cancer drugs should be administered to treat PNET has not been determined, additional predictors of their therapeutic efficacy should be investigated.