Prevalence of homologous recombination deficiency in Korean patients with epithelial ovarian cancer.

e17584 Background: The prevalence of homologous recombination deficiency (HRD) in high-grade serous carcinoma (HGSC) of epithelial ovarian cancer (EOC) is reported to be 51% in The Cancer Genome Atlas (TCGA), and 42% and 69% in Japanese and Chinese (HGSC, 87%) cohorts, respectively. As information on the prevalence of HRD in Korean patients with EOC is limited, we aimed to investigate the prevalence of HRD in Korean patients with EOC. Methods: We retrospectively analyzed data from patients with EOC who underwent GC Genome’s somatic GreenPlan HRD test up to June 30, 2024, at the National Cancer Center, Korea. Data collected included HRD status, tumor BRCA mutation ( t BRCAm) status, histology, and primary stage, and were descriptively summarized. Results: Among 538 patients with epithelial ovarian cancer, 349 patients (64.9%) were HRD. For t BRCAm status, 83 patients (15.8%) were t BRCAm+. HGSC was the most common subtype, accounting for 439 cases (81.6%). Regarding primary stage, 499 patients (92.8%) were in advanced stages. Among patients with HGSC, 71.1% (312/439) were HRD+, compared to 37.4% (37/99) among those with non-HGSC. The proportions of HRD in non-HGSC were as follows: endometrioid, 33.3% (7/21); mucinous, 100.0% (1/1); clear cell, 26.1% (6/23); low-grade serous, 9.1% (1/12), and others, including mixed and carcinosarcoma, 52.4% (22/42). Among the HRD, 84 patients (24.1%) were also t BRCAm+. Conclusions: The proportion of HRD in Korean patients with HGSC was higher than reported in TCGA and Japanese cohorts, but similar to the Chinese cohort. A substantial number of HRD cases were also identified in non-HGSC. Prevalence of homologous recombination deficiency and tumor BRCA mutation in Korean patients with epithelial ovarian cancer with comparison of results from previous studies. TCGA Japan (JGOG3025) China South Korea Number of patients, n 489(≥85% Caucasian) 711 67 538 Histology of study population HGSC All histology(HGSC, 41.9%) All histology(HGSC, 86.6%) All histology(HGSC, 81.6%) % of HRD 51% 35.2%, HGSC, 35.2%Endometrioid, 25.4%Clear cell, 11.1%LGSC, 25.0% Overall, 68.7% Overall, 64.9%HGSC, 71.1%Endometrioid, 33.3%Clear cell, 26.1%Mucinous, 100%LGSC, 9.1%Others, 52.4% Detection of HRD HR pathway gene alteration HR pathway gene alteration AmoyDxHRD panel GreenPlanHRD panel % of BRCA mutation 33%(germline or somatic) HGSC: 81.8% of BRCA1 LOF mutation and 71.4% of BRCA1 LOF mutation 35.8% in overall52.2% in HRD 15.8% in overall24.1% in HRDHGSC, 16.2%(84.5% of BRCA1/2 mutation cases) Reference TCGA Research Network, 2011 Yoshihara et al., 2023 Ni et al., 2021 Kim et al., 2024 Abbreviations: HGSC, high-grade serous carcinoma; HR, homologous recombination; HRD, homologous recombination deficiency; JGOG, Japanese Gynecologic Oncology Group; LGSC, low-grade serous carcinoma; LOF, loss of function; t BRCA , tumor BRCA.