Complete Remission with Nivolumab Monotherapy of Advanced Gastric Neuroendocrine Carcinoma

A 77-year-old man with large-cell gastric neuroendocrine carcinoma underwent palliative total gastrectomy after 10 cycles of carboplatin and etoposide chemotherapy for severe tumor bleeding. Despite a histological grade 0 therapeutic effect, the remnant lesions were treated with paclitaxel and ramucirumab, but progression occurred after two cycles. Nivolumab monotherapy was then initiated, resulting in complete remission after three cycles. Nivolumab was discontinued because of immune-related psoriasis, but complete remission persisted for at least 16 months. This is the first reported case of nivolumab monotherapy achieving complete remission in gastric neuroendocrine carcinoma with the patient surviving 28 months.