Genomic profile and clinical feature of esophageal squamous cell carcinoma, focusing on MSI, TMB, and HRD status: Analysis with the national database of Japan.

Abstract

412 Background: In Japan, cancer genome profiling (CGP) testing has been widely used from 2019, and genomic and clinical information integrated into national database (C-CAT database) is now available for secondary use for innovative research. In esophageal squamous cell carcinoma (ESCC), more than 500 patients (as of December 2022) have already undergone CGP testing. MSI-H and TMB-H ESCC are rare, and information is lacking. Using C-CAT data base, we analyzed the clinical and genomic characteristics of ESCC, especially focusing on MSI, TMB, and HRD status. Methods: We retrospectively reviewed data on 535 cases with ESCC enrolled in C-CAT between June 2019 and December 2022. The clinical features, genomic variants classified as oncogenic/pathogenic, MSI/TMB status and response to treatment (response rate; RR and time to treatment failure; TTF) were evaluated. Results: Oncogenic/pathogenic variants were detected in 527 cases (98%), and the Top 5 gene mutations were TP53 (94.6%), CDKN2A (56.6%), CDKN2B (43.7%), CCND1 (42.6%), and FGF19 (38.9%), in order of prevalence. No patient had MSI-H, and number of patients with TMB-H (≥10 Muts/Mb) and HRD were 82 (15%) and 15 (13%), respectively. Regarding the efficacy of first-line chemotherapy (IO-containing regimen in 5 cases, 0.9 %), the TTF was significantly shorter in TMB-H cases than in TMB-L cases (11.8 vs 17.5 weeks, p=0.006). No difference in response to anti-PD-1 antibody was observed depending on TMB status (RR, TMB-L 19 % vs. TMB-H 12 %). Patients with BRCA1/2 mutations tended to respond better to first-line chemotherapy including platinum drugs, although there was no difference in response to treatment with or without other HRR mutations. The percentages of cases delivered new treatments based on CGP testing was 6.8%. The percentage of cases with HRD or TMB-H suggested new treatment based on GCP testing was significantly higher than those without them. Conclusions: Patients with BRCA1/2 mutations are more sensitive to platinum combination chemotherapy and may be good candidates for PARP inhibitors in ESCC. Since TMB-H patients are resistant to standard chemotherapies, we should promote the development of immunotherapy and molecular-based targeted therapies for this population.