401. CLINICAL SIGNIFICANCE OF SIGNAL REGULATORY PROTEIN ALPHA AND CLUSTER OF DIFFERENTIATION 47 EXPRESSION IN ESOPHAGEAL SQUAMOUS CELL CARCINOMA

Abstract Background This study focuses on assessing the expression of Signal Regulatory Protein Alpha (SIRPα) and Cluster of Differentiation 47 (CD47) in Esophageal Squamous Cell Carcinoma (ESCC) and their impact on prognosis. Given the prominence of the CD47-SIRPα axis in cancer for inhibiting macrophage-mediated phagocytosis, this research aims to explore their role and significance in the development and treatment of ESCC. Methods In this study, 100 ESCC patients who underwent esophagectomy were included. Resected specimens were stained immunohistochemical staining for SIRPα and CD47. SIRPα expression was classified as high or low with cut-off value of 3%. CD47 expression was evaluated by Combined Positive Score (CPS) and Tumor Proportion Score (TPS) methods with setting a 10% threshold for high and low expression. The five-year survival rates were compared across groups over a median observation period of 61 months. This study reveals the correlation between these biomarkers and postoperative prognosis. Results Total 79 males and 21 females were included in this study and mean age was 68.7-year-old. The high SIRPα expression group (48 patients) revealed significantly worse 5-year overall survival rate than the low expression group (52 patients) (56.4 vs 82.8%, P=0.0098). For CD47, both evaluated by using CPS and TPS, the high expression group also showed significantly worse 5-year overall survival rate than its low group (48.8 vs 89.5%, P<0.0001, and 48.4 vs 87.5%, P<0.0001 respectively). Relapse free survival also showed significantly worse survival rate in high expression group of SIRPα and CD47. Conclusion The expression levels of SIRPα and CD47 serve as important biomarkers for predicting the prognosis of ESCC. They may influence prognosis by inhibiting macrophage-mediated tumor cell phagocytosis and modulating anti-tumor immune responses, offering new targets for ESCC treatment.