Homologous Recombination Deficiency and Platinum Rechallenge in Platinum-Resistant Ovarian Cancer Patients.

5576 Background: Ovarian carcinomas show homologous recombination deficiency (HRD) in up to 50% of cases and in 15 to 20% of cases occur due to germline BRCA1 or BRCA2 mutations. BRCA mutated tumors are more sensitive to PARP inhibitors and platinum based chemotherapy. The objective of this study was to characterize a cohort of ovarian cancer patients regarding HRD and to evaluate the impact of these scores in prolonged platinum sensitivity. Methods: Thirty one ovarian cancer patients with platinum resistant recurrence reexposed to platinum based chemotherapy were selected. Paraffin embedded tumor samples from 14 patients were analyzed using ONCOSCAN assay (Affymetrix) to evaluate HRD scores. The association of the scores with response rate to platinum rechallenge, overall survival and clinical pathologic factors was evaluated. Results: From the cohort of 31 patients, 15 samples from 14 patients were analyzed for genomic alterations. Median scores were 19.5 for TAI, 12.5 for cnLOH+L, 26.0 for LST and 6.3 for HRD. High scores were found in 10 out of 14 (for cnLOH+L score) and 9 out of 14 (for LST score) patients. Seven of the 14 patients analyzed analyzed for genomic alterations had response, which suggested homologous recombination deficiency. No significant differences were observed between response rates for high versus low scores. Numerically, cnLOH+L, LST and HDR scores were higher in patients with response to treatment compared to those without response. Median overall survival was 13.4 months from the beginning of platinum rechallenge and no difference in survival according to scores was observed. Among the clinical pathologic factors, family history of breast or ovarian cancer or personal history of breast cancer was associated to higher response rate to platinum rechallenge. Conclusions: In conclusion,HRD scores showed to be potential markers of response to platinum rechallenge in the platinum resistant setting. Further studies are necessary to clarify the best cutoffs for each score, the impact of tumor heterogeneity and the analysis of tumor samples in the moment of treatment. Positive family history of cancer is a clinical factor predictvie of platinum rechallenge response.