Abstract GMM-057: A FUNCTIONAL HOMOLOGOUS RECOMBINATION ASSAY PREDICTS PRIMARY CHEMOTHERAPY RESPONSE AND LONG-TERM SURVIVAL IN OVARIAN CANCER PATIENTS

PURPOSE: Homologous recombination deficiency (HRD) correlates with platinum sensitivity in ovarian cancer patients, which clinically is the most useful predictor of sensitivity to PARPi. For this reason, there is clearly a critical need to identify homologous recombination deficiency (HRD) as early as possible. Currently, HRD is mostly diagnosed by genetic testing, which however fails to identify a large proportion of HR-deficient tumors and predict a patient9s response to chemotherapy, thus we aimed to develop an ex vivo functional HRD detection test that could predict both platinum-sensitivity and patient eligibility to targeted drug treatments. METHODS: We obtained a functional HR score by quantifying homologous recombination (HR) repair after ionizing radiation-induced DNA damage in primary ovarian cancer samples (n=32). Samples clustered in 3 categories: HR-deficient, HR-low and HR-proficient. We analysed the HR score association with platinum sensitivity and treatment response, platinum-free interval (PFI) and overall survival (OS), and compared it with other clinical parameters. In parallel, we performed whole-genome sequencing and targeted DNA-sequencing of HR genes to assess if functional HRD can be predicted by currently offered genetic screening. RESULTS: Low HR scores predicted primary platinum sensitivity with high statistical significance (p=0.0103), associated with longer PFI (HR-deficient vs HR-proficient: 531 vs 53 days), and significantly correlated with improved OS (HR score CONCLUSIONS: We developed an ex vivo assay that detects tumor functional HRD and an HR score able to predict platinum sensitivity, which holds the clinically relevant potential to become the routine companion diagnostic in the management of ovarian cancer patients. Citation Format: Manuela Tumiati, Sakari Hietanen, Johanna Hynninen, Elina Pietila, Anniina Farkkila, Amjad Alkodsi, Yilin Li, Rainer Lehtonen, Erdogan Pekcan Erkan, Minna M. Tuominen, Kaisa Lehti, Sampsa K. Hautaniemi, Anna Vaharautio, Seija Grenman, Olli Carpen, and Liisa Kauppi. A FUNCTIONAL HOMOLOGOUS RECOMBINATION ASSAY PREDICTS PRIMARY CHEMOTHERAPY RESPONSE AND LONG-TERM SURVIVAL IN OVARIAN CANCER PATIENTS [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr GMM-057.