Confirmed complete response to nivolumab for advanced gastric cancer with peritoneal dissemination: a case report

Background Recent advances in cancer immunotherapy have been remarkable, with many reports on the clinical effects of immune checkpoint inhibitors. Nivolumab has been covered by the national health insurance in Japan as a third-line agent for advanced and recurrent gastric cancer since September 2017. The objective response rate for nivolumab for gastric cancer is 11.2%. However, patients' quality of life during this treatment has not been examined. Here, we report a case in which multidisciplinary treatment, including with nivolumab, resulted in long-term survival and improved quality of life. Case presentation A 70-year-old Asian woman was referred for surgery for gastric cancer. Postoperative pathological examination revealed peritoneal dissemination, and the patient was diagnosed with stage IV gastric cancer. Therefore, she was treated with S-1 and cisplatin based on negative immunohistochemical staining of resected specimens for human epidermal growth factor receptor 2. However, owing to instability and adverse events, treatment was subsequently changed to S-1 monotherapy. Two years after changing to S-1 monotherapy, she developed recurrence of peritoneal dissemination and was treated with docetaxel. Radiation therapy was also used because the recurrent lesions were local. However, 6 months later, new peritoneal dissemination and lymph node metastasis were observed and nivolumab was started. Subsequent abdominal computed tomography revealed a marked reduction in the disseminated nodules and lymphadenopathy. After 54 cycles of nivolumab, the lesions had disappeared completely. The patient has not developed side effects, including immune-responsive adverse events, has improved quality of life, and is returning to work. She is currently taking nivolumab, and there is no evidence of recurrence approximately 3 years after starting nivolumab. Conclusions Nivolumab may have beneficial effects in some patients with advanced or recurrent gastric cancer. Although the prognosis for gastric cancer and peritoneal dissemination is poor, multidisciplinary treatment that includes nivolumab may lead to long-term survival.