Case reports: chemoradiotherapy for locally advanced neuroendocrine carcinoma of the gallbladder.

Neuroendocrine carcinoma (NEC) is a rare subtype of malignant gallbladder tumor. Although surgical resection is the only potentially curative therapy for gallbladder NEC, most cases are surgically unresectable because of advanced stage disease and/or biologically aggressive behavior. The standard palliative treatment for malignant gallbladder tumors is chemotherapy; however, the efficacy of chemoradiotherapy in the treatment of gallbladder tumors is controversial. Here, we report a case of gallbladder NEC that showed a durable response to chemoradiotherapy. A 68-year-old Japanese man presented with a huge gallbladder tumor with liver and duodenal invasion. Pathological findings revealed poorly differentiated NEC of the gallbladder. After seven cycles of chemotherapy comprising cisplatin and irinotecan, computed tomography (CT) revealed remarkable tumor shrinkage, but an enlarged portal lymph node. The patient was treated with 50.4 Gy in 28 fractions with two cycles of cisplatin and etoposide. After chemoradiotherapy, the enlarged lymph node also decreased in size. Maximum standardized uptake value of fluorodeoxyglucose-positron emission tomography/CT(FDG-PET/CT) changed from 8.2 to physiological accumulation. We defined this condition as a complete response on both enhanced CT and FDG-PET/CT; therefore, we did not perform systemic treatment and only observed his condition. This patient remained healthy with no recurrence at 3 years after chemoradiotherapy.