Objective:The predictive effect of preoperative chemoradiotherapy(CRT)is low and difficult in guiding individualized treatment.We examined a surrogate endpoint for long-term outcomes in locally advanced gastric cancer patients after preoperative CRT.Methods:From April 2012 to April 2019,95 patients with locally advanced gastric cancer who received preoperative concurrent CRT and who were enrolled in three prospective studies were included.All patients were stage T3/4N+.Local control,distant metastasis-free survival(DMFS),disease-free survival(DFS)and overall survival(OS)were evaluated.Clinicopathological factors related to long-term prognosis were analyzed using univariate and multivariate analyses.The down-staging depth score(DDS),which is a novel method of evaluating CRT response,was used to predict long-term outcomes.Results:The median follow-up period for survivors was 30 months.The area under the curve(AUC)of the receiver operating characteristic(ROC)curve predicted by the DDS was 0.728,which was better than the pathological complete response(pCR),histological response and ypN0.Decision curve analysis further affirmed that DDS had the largest net benefit.The DDS cut-off value was 4.pCR and ypN0 were associated with OS(P=0.026 and 0.049).Surgery and DDS are correlated with DMFS,DFS and OS(surgery:P=0.001,＜0.001 and＜0.001,respectively;and DDS:P=0.009,0.013 and 0.032,respectively).Multivariate analysis showed that DDS was an independent prognostic factor of DFS(P=0.021).Conclusions:DDS is a simple,short-term indicator that was a better surrogate endpoint than pCR,histological response and ypN0 for DFS.