Objective:Prognosis of patients with locally advanced rectal cancer (LARC) but achieving ypT1-2N0 stage after neoadjuvant concurrent chemo-radiotherapy (CRT) has been shown to be favorable.This study aims to determine whether the long-term outcome of ypT1-2N0 cases can be comparable to that of pT1-2N0 cohort that received definitive surgery for early disease.Method:From January 2008 to December 2013,449 consecutive patients with rectal cancer were treated and their outcome maintained in a database.Patients with LARC underwent total mesorectal excision (TME) surgery at 4-8 weeks after completion of CRT,and those achieving stage ypI were identified as a group.As a comparison,stage pI group pertains to patients whose initially limited disease was not upstaged after TME surgery alone.After propensity score matching (PSM),comparisons of local regional control (LC),distant metastasis-free survival (DMFS),disease-free survival (DFS) and overall survival (OS) were performed using Kaplan-Meier analysis and log-rank test between ypI and pI groups.Down-staging depth score (DDS),a novel method of evaluating CRT response,was used for subset analysis.Results:Of the 449 patients,168 matched cases were generated for analysis.Five-year LC,DMFS,DFS and OS for stage pI vs.ypI groups were 96.7％ vs.96.4％ (P=0.796),92.7％ vs.73.6％ (P=0.025),91.2％ vs.73.6％ (P=0.080) and 93.1％ vs.72.3％ (P=0.040),respectively.In the DDS-favorable subset of the ypI group,LC,DMFS,DFS and OS resulted in no significant differences in comparison with the pI group (P=0.384,0.368,0.277 and 0.458,respectively).Conclusions:LC was comparable in both groups;however,distant metastasis developed more frequently in down-staged LARC than de novo early stage cases,reflecting the need to improve the efficacy of systemic treatment despite excellent pathologic response.DDS can be an indicator to identify a subset of the ypI group whose long-term oncologic outcomes are as good as those of stage pI cohort.