A Case of Gastric Cancer with Pathological Complete Response after Chemotherapy Using S-1, Oxaliplatin, and Nivolumab

Abstract

A 59-year-old man presented with epigastric pain and nausea. Upper gastrointestinal endoscopy revealed a type 2 lesion in the upper gastric angle to the lesser curvature of antrum of the stomach, and it was histologically diagnosed as moderately differentiated adenocarcinoma. Abdominal enhanced CT scan in our hospital revealed the cancer to be cT4a (SE) N+M0 cStage III with direct invasion of metastatic lymph nodes to the common hepatic artery. The patient underwent systemic chemotherapy with S-1+oxaliplatin (SOX) +nivolumab regimen. Subsequent enhanced CT imaging after four cycles of the treatment showed a reduction in the primary lesion and lymph node metastases, prompting a decision for conversion surgery. The procedure involved open total gastrectomy with D2 lymphadenectomy. Histological evaluation of the resected specimen indicated Grade 3 histological effect with pathological complete response (pCR). This case represents a successful pCR achieved through SOX+nivolumab therapy for initially unresectable gastric cancer, followed by conversion surgery.