Genomic profiling of Chinese esophageal squamous cell carcinoma patients and difference of genomic mutation between Chinese and American cohorts.

e16108 Background: Esophageal squamous cell carcinoma (ESCC) remains an aggressive malignancy and most patients are diagnosed at advantage stage with limited treatments. Large amount of evidence has demonstrated that immune biomarkers such as PD-l/PD-L1 and tumor mutational burden (TMB) are associated with clinical outcomes and disease prognosis. Methods: A total of 475 ECSS patients enrolled in this study. Deep sequencing of 450 cancer genes performed on formalin-fixed paraffin-embedded tumor tissues and matched blood. Results: Genomic mutation landscape indicated the top five mutated genes are TP53 (95.0%), CCND1 (42%), FGF3 (42%), FGF19 (41%), FGF4（41%. We found that CCHD2, FOXL2 and PIK3CA were tumor-driver genes in 475 ECSS patients. BCL6 ( p< 0.02), CCND1 ( p< 0.03), FGF12 ( p< 0.04), FGF19 ( p< 0.04), FGF3 ( p< 0.02) and FGF4 ( p< 0.05) mutations are significantly associated with high expression of PD-L1 Moreover, we found that BCL6 ( p< 0.04), BRD4 ( p< 0.03), EP300 ( p< 0.03), HGF ( p< 0.02), KMT2C ( p< 0.005), KMT2D ( p< 0.04), MET ( p< 0.006), NSD1 ( p< 0.04), PBRM1 ( p< 0.003), PTCH1 ( p< 0.01), SPEN ( p< 0.006), SPTA ( p< 0.02), ZHF750 ( p< 0.004), TP53 ( p< 0.01) mutation are significantly associated with high TMB as well. The cutoff for TMB is set for 6.9 mut/Mb. The target gene analysis indicated that over half of Chinese ECSS patient might benefit from gene target therapy. By comparison between Chinese and TCGA cohorts, EBFR ( p< 0.05), FGRF1 ( p< 0.05) and CDKN2A ( p< 0.001) have significantly mutated frequency, which indicated the gene mutated profiling is significantly different between Chinese and American ECSS patients. Conclusions: This study identified certain gene alteration associated with PD-L1 and TMB status. It is necessary to conduct large clinical study to identify biomarker for evaluation the efficacy of novel adjunct immunochemotherapy.