PS02.085: ASSESSMENT OF TUMOR REGRESSION OF ESOPHAGEAL SQUAMOUS CELL CARCINOMA AFTER NEOADJUVANT CHEMORADIOTHERAPY: COMPARISON OF 3 COMMONLY USED SCORING APPROACHES

Background Tumor regression grade (TRG) is a measure of histopathological response of cancer to neoadjuvant chemoradiotherapy(nCRT) and is associated with outcomes. Several TRG system are used in esophageal cancer: Schneider 4 tier(0%,1∼10%,10∼50%, > 50% vital residual tumor cell[VRTC]), Chirieac 3 tier(0%,1∼50%, > 50% VRTC) and Japanese 4 tier(0%,1∼33%,33∼66%, > 66% VRTC). Although these methods are generally accepted, currently there is no common standard. Methods We compared the application of three major systems for assessment of tumor regression. Hematoxylin and eosin–stained slides from 370 resection specimens of esophageal squamous cell carcinoma following nCRT were independently reviewed by two pathologists. Primary endpoints included (1) interobserver agreement (2) prognostic discrimination Results Interobserver agreement was excellent for all three sutem while the Chirieac 3 tier system showed the best kappa value(0.93). All models had similar discriminatory and stratification power, and they predicted survival (P < 0.0001) on univariate analysis. While Chirieac system remained a significant predictor for overall survival independent of yp-stage and margin status in multivariate analysis. Conclusion A simple 3-tiered system with the estimation of VRTC(0%,1∼50%, > 50%) is most reproducible for the evaluation of histological response and together with yp-stage and margin status as independent predictors for survival. Disclosure All authors have declared no conflicts of interest.