[Long-Term Survival of an Adolescent and Young Adult Patient with Unresectable Advanced Gastric Cancer in Whom Multidisciplinary Treatment Was Effective].

We report the case of a long-term-surviving adolescent and young adult patient with unresectable advanced gastric cancer for whom multidisciplinary treatment was effective. A 29-year-old woman was referred to our hospital for further examination following a diagnosis of gastric cancer by a local physician. Esophagogastroduodenoscopy showed a deep ulcerated lesion in the lower third of the stomach, and analysis of biopsy specimens revealed an adenocarcinoma. Abdominal contrast- enhanced computed tomography showed gastric wall thickening in the lower third of the stomach. The patient underwent distal gastrectomy with lymph node dissection, including resection of localized peritoneal metastases, followed by Roux-en- Y reconstruction. The pathological diagnosis was serosa-invading poorly differentiated adenocarcinoma with 1 lymph node metastasis measuring 6.0×5.5 cm in the posterior wall of the lower third of the stomach and negative immunohistochemical staining for human epidermal growth factor receptor 2. The patient received postoperative chemotherapy with S-1 and oxaliplatin. She developed bilateral ovarian metastases measuring 13.0 cm and 7.8 cm after 17 months. The patient presented with severe lower abdominal pain and underwent an emergency bilateral ovarian metastasectomy, which revealed torsion of the right ovarian tumor, which had twisted twice on its pedicle, and a left ovarian mass. After the operation, 41 courses of ramucirumab with nab-paclitaxel were administered as a second-line treatment, and she received systemic drug treatment. Sixty months after the gastrectomy, the patient developed left hydronephrosis due to peritoneal metastases and was treated with nivolumab after ureteral stent replacement. No effective treatment was proposed in cancer multigene panel testing, and she died 66 months after the initial treatment because of disease progression. Comprehensive multidisciplinary treatment, including surgical and local therapy for peritoneal dissemination based on drug therapy for unresectable advanced gastric cancer, may result in long-term survival. Further research and accumulation of such cases would lead to the development of novel treatments.