Impact of pathogenic germline variants in HRR genes on gastroesophageal cancer in a large real-world Chinese population: A comprehensive study.

Abstract

10588 Background: Genetic testing in gastroesophageal cancer has been limited to those with hereditary cancer syndromes, restricting understanding of the impact of germline variants in sporadic cancers. Our study expands this by exploring germline and somatic characteristics in a broad Chinese cohort, enhancing risk assessment and guiding treatment strategies in a wider population. Methods: From October 2017 to April 2023, we retrospectively analyzed 2596 Chinese gastroesophageal cancer (GEC) patients, including 2003 with gastric cancer (GC), 196 with gastroesophageal junction cancer (GEJC), and 397 with esophageal cancer (EC). A 520-gene panel including 62 genes associated with cancer predisposition, was employed for genomic profiling of paired tumor and white blood cell samples. The pathogenicity of germline variants was determined according to ACMG guidelines. Results: In this retrospective cohort, the proportion of patients carrying pathogenic/likely pathogenic (P/LP) germline variants was 5.3% in GC, 5.6% in GEJC, and 5.0% in EC, respectively. Notably, genes associated with HRR exhibited the highest rates of P/LP germline mutations in GEC (94, 3.7%), with the majority occurring in non-BRCA HRR genes (77, 3.0%). The top five genes with the highest mutation rates were ATM, PALB2, FANCA, CHEK2, and RAD54L. Compared to the East Asian population without cancer in the genomAD database, a higher proportion of P/LP germline mutations were found in the CDH1(Inf [6.46-Inf], p < 0.001), PALB2 (5.60 [1.61-13.09], p = 0.002), SDHA (8.99 [1.29-99.42], p = 0.012), ATM (2.15 [1.08-4.09], p = 0.02), and CHEK2 (3.83 [1.06-13.32], p = 0.02) genes in GC. Similarly, significant increases in PALB2 (10.36 [2.32-37.28], p = 0.002) and ATM (4.42 [0.86-14.33], p = 0.036) were also observed in EC and GEJC. The HRR P/LP variant group exhibited a higher incidence of biallelic inactivation (loss of wildtype allele) compared to the B/LB variant group (24.7% vs 6.6%, p<0.001). Moreover, the similar trend was observed for the moderately/uncertainly penetrant gene ATM and FANCA (38.5% vs 0.6%, p < 0.001; 42.9% vs 9.8%, p = 0.025), which suggests that ATM and FANCA may be associated with a high risk. The HRR genes ATM(56 vs 61, p = 0.052), CDH1(33 vs 61, p = 0.003), and FANCI(48 vs 61, p = 0.041) with P/LP variants were associated with a younger age of onset. Carriers of HRR P/LP variants had less prevalent somatic TP53 variants in GC and GEC and higher HRD score compared to non-carriers (p=0.005). Conclusions: Our research delineates the germline P/LP variant landscape in Chinese GEC, revealing the significant role of HRR P/LP variants. The presence of P/LP variants in HRR genes in GEC is linked to distinct disease characteristics and progression, underscoring their importance in guiding personalized treatment approaches and risk evaluation.