246. SPATIAL HETEROGENEITY OF PD-L1 EXPRESSION INFLUENCE ITS ASSESSMENT IN ESOPHAGEAL SQUAMOUS CARCINOMA (ESCC)

Abstract Background Anti-PD-1/PD-L1 immunotherapy is a promising treatment for ESCC. High PD-L1 expression theoretical predictive biomarker, but the poor response also observed in some patients with high expression. Biopsies assessment of always focuses on single region which may be influenced by spatial heterogeneity tumor microenvironment. This study investigates whether biopsy different regions related to its paradoxical value. Methods We prospectively included 30 consecutive treatment-naïve, stage II-III ESCC who underwent upfront esophagectomy. Multi-region sampling was taken endoscopic forceps (Fig. A) from four (A/B/C/D) proximal, distal, midpoint surface, and internal center, respectively. Each spaced ≥1 cm apart avoided areas severe necrosis. compared at endoscopic-biopsy overall surgical-resected specimen. evaluated immunohistochemistry using combined positive score (CPS). negative defined as CPS ≥ 1 < 1, Results Based tumor, were 66.7% 10% patients, positive/negative discordance rate concordance (kappa = 0.206) B). Correlations between C) revealed B D (r 0.77) relatively low others. Combining multi-region evaluation improved correlation consistency D). Comparing based gold standard specimen, sensitivity increased 12.5% versus single-region assessment. Conclusion spatially heterogeneous ESCC, cannot reflect status consistent observation suboptimal prediction immunotherapy. could help improve bias heterogeneity, identification candidate