Conversion surgery for stage IV gastric cancer: Real-world insights with a focus on elderly patients (OGSG2301).

311 Background: Recent advances in systemic chemotherapies, especially molecular targeted drugs and immune checkpoint inhibitors (ICIs), have improved survival outcomes for patients with Stage IV gastric cancer. However, their impact on conversion surgery rates remains unclear, particularly in elderly patients. Methods: This study retrospectively analyzed 376 Stage IV gastric cancer patients treated with chemotherapy across 36 institutions in 2022. The primary endpoint was the overall conversion surgery rate, defined as any surgery performed after chemotherapy. The conversion surgery rate according to the JCOG criteria was also evaluated as a secondary endpoint; this refers to surgery performed on patients whose tumors were converted from unresectable to resectable status as a result of chemotherapy. Additionally, the following data were compared between the elderly (≧75 y.o.) and non-elderly groups (<75 y.o.): conversion surgery rate, patients’ characteristics, chemotherapy information, and surgical data. Overall survival was analyzed and compared between patients who underwent conversion surgery and those who did not in both the elderly and non-elderly groups. Subgroup analyses identified factors influencing conversion surgery eligibility in elderly patients. Results: Among 376 patients, 126 (33.5%) and 250 (66.5%) patients were classified as elderly and non-elderly group, respectively. Performance status scores were as follows: score 0 was observed in 42.9% of the elderly group and 59.5% of the non-elderly group; score 1 was observed in 48.4% and 35.2%, respectively. Conversion surgery rates were 12.7% in elderly patients and 20.4% in non-elderly patients (p = 0.086). Among HER2-negative cases treated with ICI, the conversion surgery rate according to JCOG criteria was significantly lower in the elderly group (4.1%) than in the non-elderly group (12.9%) ( p = 0.039). In contrast, among HER2-positive cases, the conversion surgery rates by JCOG criteria did not significantly differ between the elderly and non-elderly groups (11.8% for both groups, p = 1.0). Postoperative complications were more frequent in elderly patients but without significant differences (31.2% vs 17.6%, p = 0.295). There was no reported mortality across all surgical cases. The 2-year overall survival rates for resected versus unresected cases were 87.5% vs. 21.5% in the elderly group, and 82.2% vs. 28.4% in the non-elderly group (both p < 0.001). Among elderly patients with PD-L1combined positive score≧5, cT1-3, Yoshida’s classification category 1, and distant lymph node metastasis, conversion surgery rates exceeded 20%. Conclusions: Elderly patients with Stage IV gastric cancer could be considered as potential candidates for conversion surgery under careful selection to improve treatment outcomes.