RAD51 foci predict chemotherapy response better than genomic scars in high-grade serous ovarian cancer

Homologous recombination (HR)-deficiency has been suggested as a marker of chemotherapy sensitivity. The current standard is to use genome-based assays to define tumors as HR-deficient (HRD) or HR-proficient (HRP). However, these scars do not represent the current functional state of the tumor and thus inconsistently correlate with treatment response. Here, we propose RAD51 binding, a late step in HR, as a functional readout of HR status. Our objective was to evaluate the ability of RAD51 foci to predict chemotherapy response in pre-treatment high-grade serous ovarian cancer (HGSOC) samples and compare the predictive performance of this assay to standard-of-care genomic assays.