[Perioperative Treatment for Gastric Cancer Using Immune Checkpoint Inhibitors].

Perioperative and adjuvant treatment for resectable gastric cancer was historically fragmented across regions. In East Asia, high-quality D2 gastrectomy followed by postoperative chemotherapy became the standard, whereas postoperative chemoradiotherapy was established in North America and perioperative chemotherapy was developed in Europe. Over the past 2 decades, surgical quality in Western countries has improved, particularly through wider adoption of D2 lymphadenectomy, and perioperative chemotherapy has evolved from ECF/ECX to FLOT. The global phase Ⅲ MATTERHORN trial marked a major turning point. Perioperative durvalumab plus FLOT followed by adjuvant durvalumab significantly improved event-free survival compared with FLOT alone, establishing the D-FLOT strategy as a new global standard. In Japan, this regimen was approved in June 2026 and has become an important treatment option. Nevertheless, several issues remain when applying the trial results to Japanese practice. Gastric cancer incidence is decreasing, while the patient population is rapidly aging. Clinical staging remains imperfect, and routine use of D-FLOT in all patients with clinical stage Ⅱ disease may result in overtreatment. Safe delivery of FLOT requires multidisciplinary expertise, proactive supportive care, nutritional management, and close collaboration between surgeons and medical oncologists. For MSI-high or mismatch repair-deficient gastric cancer, neoadjuvant immune checkpoint blockade has produced high pathological complete response rates, raising the possibility of chemotherapy-free treatment and future non-operative management. However, response rates in gastric cancer are less uniformly high than those observed in rectal cancer, and accurate confirmation of complete response in both the primary tumor and regional lymph nodes remains challenging. Thus, organ preservation in gastric cancer should still be investigated in prospective clinical trials. This review summarizes the historical evolution, evidence from MATTERHORN, practical challenges in Japan, and future directions for biomarker-driven de-escalation.