[Locally Advanced Gastric Cancer Showing Marked Tumor Shrinkage after the First Dose of Nivolumab for Fourth-Line Chemotherapy].

We report a case of locally advanced gastric cancer, which showed marked tumor shrinkage after the first dose of nivolumab. A 75-year-old woman was diagnosed with locally advanced gastric cancer with pancreatic invasion and pyloric stenosis. We performed gastrojejunostomy before chemotherapy. The first-line, second-line, and third-line chemotherapies were not effective, resulting in tumor progression and necrosis with abdominal wall penetration. Her performance status was good, so we started nivolumab therapy as the fourth-line chemotherapy. Nine days after the first dose of nivolumab, she had a severe abdominal pain and a sense of fatigue. CT imaging showed a remarkable degree of tumor necrosis just beneath the skin. We diagnosed progressive disease and discontinued the chemotherapy. However, her general condition gradually improved and CT imaging 4 months after the first dose of nivolumab showed marked tumor shrinkage. We restarted nivolumab therapy and she has been alive for 2 years 10 months since the introduction of chemotherapy. It was suggested that a single dose of nivolumab only could lead to marked tumor shrinkage in chemotherapy for advanced gastric cancer.