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 32 mm in diameter. We planned to perform subtotal stomach-preserving
pancreaticoduodenectomy, but abandoned resecting the pancreas during the surgery upon discovering a small liver
tumor 3 mm 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 5 weeks 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 7 months, but the patient developed
interstitial pneumonia and experienced metastatic progression. Subsequent
sunitinib administration for 6 months was ineffective. Finally, we chose STZ (1000 mg/m2, weekly) as a third-line treatment, which produced a partial response for 10 months. The patient remains alive 38 months 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.