[Brain Metastasis Arising from Gastric Cancer during Long-Term Treatment Using Nivolumab].

Metastasis to the central nervous system from gastric cancer is exceedingly uncommon. We report a gastric cancer patient with cerebral metastasis during the period when durable response was obtained by systemic drug treatment using nivolumab. A 78-year-old male was referred to our hospital for further examination following diagnosis of gastric cancer by a local medical doctor. Esophagogastroduodenoscopy showed a slightly elevated lesion with central depressed area in the upper-third of the stomach, and analysis of biopsy specimens revealed an adenocarcinoma. The patient underwent laparoscopic total gastrectomy with lymph nodes dissection followed by Roux-en-Y reconstruction, resulting in submucosal invasive carcinoma and no lymph node metastasis. The patient developed solitary splenic metastasis measuring 4.2 cm after 28 months later, and the patient underwent a splenectomy, since there was no evidence of further metastatic lesions in any other organs. Subsequently, the patient was received S-1 plus oxaliplatin chemotherapy based on negative immunohistochemical staining of the resected specimens for human epidermal growth factor receptor 2. Four months after the splenectomy, the patient developed multiple liver metastases and was treated with ramucirumab plus paclitaxel. Because of disease progression, the patient was administered 3 mg/kg, iv, nivolumab every 2 weeks. After 4 courses of systemic treatment using nivolumab, abdominal computed tomography revealed marked shrinkage of the liver metastases. After 12 courses of nivolumab, the liver metastases had disappeared completely. The patient developed hypothyroidism, which could be controlled by thyroid hormone replacement treatment. The patient continues to receive nivolumab, and there is no evidence of disease recurrence in the 33 month period since starting nivolumab. However, he developed cerebral metastases after 69 months after surgery, complaining of articulation disorder. The patient underwent tumor resection by craniotomy followed by radiation therapy; however, he died 3 months after the operation. Although brain metastasis arising from gastric cancer is rare, future identification of risk factors and development of novel treatments are desired by further investigations and accumulation of these cases.