ASO Visual Abstract: Conversion Surgery After Chemotherapy Plus Nivolumab as the First-Line Treatment for Unresectable Advanced or Recurrent Gastric Cancer and a Biomarker Study Using the Gustave Roussy Immune Score-A Multicenter Study

Background. There are few reports on conversion surgery (CS) after chemotherapy plus nivolumab as a first-line treatment in patients with unresectable advanced or recurrent gastric cancer (GC). This multicenter study was conducted to analyze real-world data on CS after chemotherapy plus nivolumab as a first-line treatment and to identify predictive biomarkers. Methods. This multicenter study included 104 patients who received chemotherapy plus nivolumab as primary treatment for unresectable advanced recurrent GC from 12 institutes. We investigated and analyzed patient characteristics and blood test data in the presence or absence of CS, the relationship between the Gustave Roussy Immune Score (GRIm-s) and CS, and the characteristics of CS cases. Results. CS was performed in 12 patients (11.5%). Eastern Cooperative Oncology Group Performance Status (ECOG-PS) was significantly better in patients who underwent CS (p < 0.0001). There were no CS cases with high-risk GRIm-s (0%), however there were 22 non-CS cases (23.9%). No high-risk GRIm-s cases were converted to CS. Minimally invasive surgery was performed in 50.0% of the cases, with R0 resection in all cases and only one case of urinary retention (Grade II) as a postoperative complication, indicating a good postoperative short-term outcome. There were two cases of postoperative recurrence (16.7%), both of which were grade 1b. Conclusions. The short-term postoperative results of CS after chemotherapy plus nivolumab as the first-line treatment for GC were acceptable in this study. There were no high-risk GRIm-s cases among those who underwent CS, suggesting that the GRIm-s may be a predictor of CS.