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Abstract Background Advanced gastric cancer has an unfavorable prognosis and poor curability. Immune checkpoint inhibitors, such as nivolumab, have recently emerged as a potential solution for this aggressive disease. However, there is a lack of established evidence on the clinical efficacy of these agents, particularly in the perioperative period for advanced gastric cancer patients who are unresectable, recurrent, or preoperative. Despite the limited data available, there have been rare cases of dramatic therapeutic effects. In this study, we present a successful case of nivolumab treatment along with surgery. Case presentation A 69-year-old female presented with pericardial discomfort and was diagnosed with advanced gastric cancer following upper gastrointestinal endoscopy. Laparoscopic distal gastrectomy with D2 lymph node dissection was performed, resulting in a final pathological diagnosis of Stage IIIA. The patient received postoperative adjuvant chemotherapy with oral S-1 therapy, but was found to have multiple liver metastases at 8 months postsurgery. Weekly paclitaxel and ramucirumab therapy was initiated, but the patient experienced adverse side effects, leading to the discontinuation of treatment. Nivolumab monotherapy was then administered for 18 cycles, resulting in a partial therapeutic response and PET–CT revealed a complete metabolic response. However, the patient developed a Grade 3 pemphigoid as an immune-related adverse event, leading to the cessation of nivolumab. The patient underwent laparoscopic partial hepatectomy. Postoperative pathology showed no residual tumor cells, indicating a complete response. At present, 25 months after surgery, the patient was alive without recurrence. Conclusion In this report, we present a case of gastric cancer with liver metastatic recurrence, in which a complete pathological response was achieved with nivolumab treatment. Although determining whether surgical intervention is necessary following successful drug treatment can be challenging, PET–CT imaging may be useful in decision-making regarding surgical treatment.

Abstract Background Local resection is the standard treatment for gastrointestinal stromal tumors (GISTs). Laparoscopic and endoscopic cooperative surgery (LECS) is a minimally invasive surgery used to resect GISTs. Herein, we report an extremely rare case of a gastric GIST that grossly vanished during LECS. Case presentation A 50-year-old Japanese female was referred to our hospital after an abnormality was detected during an esophagogastroduodenoscopy (EGD) at her annual health checkup. Based on EGD, endoscopic ultrasound (EUS), and computer tomography (CT) findings, the patient was diagnosed with a 50-mm submucosal tumor (SMT) with intraluminal growth on the anterior wall of the lesser curvature of the upper body of the stomach. We routinely use LECS to treat the intraluminal growth type of GISTs. During the intraoperative endoscopy, the intraluminal submucosal tumor, which was detected preoperatively, had vanished. A red-white scar was observed in the regressed tumor region. LECS was performed by resecting at a distance away from the scar tissue and closing the gastric wall with intracavitary sutures. In the evaluation from the tumor section view of the original resected specimen, a 22 × 14 × 8 mm lobular neoplasm was observed that was predominantly located in the gastric submucosa to the muscularis propia. Pathological findings confirmed the diagnosis of GIST with intermediate risk indicated by the Fletcher classification. The patient continued postoperative adjuvant chemotherapy with imatinib and no recurrence was detected over 12 months after surgery. Conclusion LECS was performed on the vanished gastric GIST, providing the best surgical treatment and leading to an accurate diagnosis and optimal postoperative care.