A case of gastric cancer that developed thrombocytopenia during treatment with nivolumab.

A 72-year-old man was treated by two-regimen chemotherapies for unresectable advanced gastric cancer with metastatic lymph nodes near the pancreatic head, followed by the third-line chemotherapy using nivolumab (Nivo). Ten days after the two-course Nivo chemotherapy, grade 4 thrombocytopenia (TCP) occurred according to the Common Terminology Criteria for Adverse Events. He was treated by steroid and Helicobacter pylori (HP) eradication therapies. Consequently, the platelet count improved rapidly without any complications. Before resuming the Nivo therapy, the platelet count was already improved. Fourth-line chemotherapy was then started using irinotecan. After three courses, his general condition worsened. Unfortunately, the patient died 18 months after gastric cancer diagnosis. Although rare, severe TCP is potentially a fatal complication of chemotherapy using immune checkpoint inhibitors. In addition to standard treatment with steroids, HP eradication therapy may be effective for Nivo-associated TCP.