[A Case of Brain Metastasis of Gastric Cancer Successfully Treated with Nivolumab].

A 68‒year‒old man was referred to our hospital due to vomiting and light‒headedness. The patient was diagnosed with advanced gastric cancer. Neoadjuvant chemotherapy(S‒1 plus oxaliplatin)was initiated resulting in a partial response(PR) after 5 courses. Total gastrectomy and D1 dissection was performed. The tumor was diagnosed as poorly differentiated adenocarcinoma and the pathological Stage was ypT3, N3b, M1[CY1], ypStage Ⅳ. Ramucirumab plus nab‒paclitaxel was administered due to the appearance of swollen lymph nodes post‒operatively. This treatment maintained PR for 6 courses. However, after an evaluation of progressive disease(PD), nivolumab was initiated as third‒line chemotherapy. After 3 courses, a sudden seizure occurred and a brain metastasis with a diameter of 6 mm was observed. Considering the decrease in CEA level and that the brain metastasis presented as a small lesion, the tumor was inferred to be highly sensitive to nivolumab. We continued nivolumab monotherapy as chemotherapy. Radiotherapy was not performed. Both intra and extra‒cranial metastatic lesions maintained PR for 17 courses. The treatment was changed to irinotecan after evidence of PD was observed. However, after 2 courses(2 years and 3 months from his first visit), the patient died of an unknown cause. To our knowledge, this is the first case of brain metastasis of gastric cancer successfully treated with nivolumab.