Homologous recombination deficiency score for predicting efficacy of platinum-based chemotherapy and PARPi maintenance therapy in ovarian cancer.

e17543 Background: Currently, homologous recombination deficiency (HRD) has been confirmed to be a predictive biomarker for poly-ADP-ribose-polymerase inhibitors (PARPi) in ovarian cancer, while its effects on the clinical outcomes of platinum-based chemotherapy and PARPi maintenance therapy are not assessed rigorously in ovarian cancer. We developed an HRD assay to evaluate the effect of HRD scores on the platinum-based chemotherapy and PARPi maintenance therapy in Chinese patients with ovarian cancer. Methods: HRD testing was performed on the samples obtained at primary cytoreductive surgery. The progression-free survival (PFS) was observed among the BRCA-mutated/HRD-positive and BRCA wild-type/HRD-negative patients. Univariate and multivariate COX analyses were performed to test the association of PFS with different variables, and hazards ratios (HR) and 95% confidence interval (CI) were calculated. The two-tailed p value less than 0.05 was considered statistically significant. Results: Totally 74 patients who received platinum-based chemotherapy were eligible for the study, among whom 81.1% responded to the initial platinum-based chemotherapy, 33.8% harbored BRCA1/2 mutations and 74.3% were HRD-positive. The median HRD score of platinum-sensitive patients (n=60) was 48.5, significantly higher than the 31 of platinum-resistant patients (n=14, p=0.0035). Analysis of loss of heterozygosity (LOH), telomeric allelic imbalance (TAI) and large-scale state transitions (LST) between platinum-sensitive and platinum-resistant patients showed significant differences in TAI ( p=0.0012) and LST ( p=0.004). Compared with HRD-negative patients, HRD-positive patients had a significantly longer median PFS (10 vs. 15 months, p=0.017), and multivariate analysis further indicated that HRD-positive status (HR, 0.423, 95%CI: 0.191-0.939, p=0.035) was a significant predictor for the improvement of PFS. Conclusions: The HRD assay developed in our study can accurately predict the response to platinum-based chemotherapy and PARPi efficacy in patients with ovarian cancer, providing powerful evidence for implementation of genetic testing and guidance of clinical treatment in ovarian cancer.