Gastric adenocarcinoma is concurrent with metastatic neuroendocrine cancer treated with nivolumab and chemotherapy: A case report.

Gastric adenocarcinoma concurrent with metastatic neuroendocrine cancer (NEC) is rare. In the present case report, a 39-year-old male was first pathologically diagnosed by gastric endoscopy as having a highly differentiated adenocarcinoma. Next, positron emission tomography-computed tomography examination and bone marrow biopsy confirmed extensive metastasis. Subsequently, the patient underwent 6 cycles of immunotherapy (nivolumab, 160 mg) and 5 cycles of chemotherapy based on the XELOX regimen (oxaliplatin + capecitabine). Following this, the patient received the final cycles of nivolumab and XELOX; however, the patient then succumbed. Further biopsy of the metastatic collarbone lymph nodes indicated NEC. Overall, the progression-free survival was ~3.5 months, and overall survival (OS) was ~6 months. The case presented the possibility of concurrent gastric adenocarcinoma and NEC in the clinic. In addition, the efficacy of a combined regimen such as immunotherapy and chemotherapy for such disorders still requires further validation in the future.