Five-year overall survival with S-1 plus docetaxel as adjuvant treatment in curatively resected pStage III gastric cancer in JACCRO GC-07

4065 Background: JACCRO GC-07 is a randomized controlled trial to explore postoperative S-1/docetaxel compared to S-1 alone after D2 gastrectomy for pStage III gastric cancer (GC) patients. The second interim analysis demonstrated that the significant improvement of RFS was obtained by S-1/docetaxel compared to S-1 alone. The study was terminated by the recommendation of independent data and safety monitoring committee (Yoshida K et al. J Clin Oncol 2019; 37:1296-1304). Preplanned analysis to evaluate RFS at 3 years, the primary endpoint, was also published (Kakeji Y et al. Gastric Cancer 2022; 25:186-196). We report the 5-years follow-up data from the trial. Methods: Patients with pStage III GC were randomly assigned to receive either S-1/docetaxel (S-1 80-120mg/body on days 1-14 with a 7-day rest followed by docetaxel 40mg/m 2 on day 1 and S-1 80-120mg/body on days 1-14 every 21 days for 6 cycles followed by S-1 80-120mg/body on days 1-28 every 42 days for 4 cycles) or S-1 (80-120mg/body on days 1-28 every 42 days for 8 cycles) after D2 gastrectomy. Blocked randomisation was performed and stratified by the stage (IIIA, IIIB, IIIC) and histological type (differentiated or undifferentiated). The primary endpoint was 3y RFS and the secondary endpoints were OS, TTF and safety. This analysis presents the final preplanned assessment of outcomes after 5 years. Results: Of 915 randomly assigned patients, 912 patients were included in the intention-to-treat (ITT) analysis. In the final analysis, 426 recurrences and 373 deaths were confirmed among the ITT population during the median follow-up period of 63.72 months (3.52-111.87). The 5y RFS of 59.8% in the S-1/docetaxel group was significantly superior to 50.6% in the S-1 group (HR 0.726, 95% CI: 0.599-0.879, p = 0.0010) and the 5y OS was 67.9% in the S-1/docetaxel group and that of S-1 group was 60.3%, respectively (HR 0.752, 95% CI: 0.613-0.922, p = 0.0059), confirming the significant improving effect on the survival of the patient. Conclusions: Adjuvant treatment with S-1 plus docetaxel should be considered for patients with pStage III gastric cancer who underwent D2 gastrectomy without neoadjuvant chemotherapy. Clinical trial information: UMIN000010337 .