Predicting Olaparib Sensitivity in Patients With Unresectable Locally Advanced/Metastatic HER2-negative Breast Cancer.

The primary objetive is to assess the capacity of the RAD51-foci score to predict the efficacy of olaparib in BRCA1/2, PALB2 or RAD51C/D mut advanced breast cancer (cohort 1). The investigators propose the hypothesis that the RAD51-foci low tumours determined by immunofluorescence using RAD51 assay in patients with BRCA1/2, PALB2 \& RAD51C/D mutation (cohort 1) predicts response to olaparib. Furthermore, The investigators posit that the determination of RAD51-foci score in tumour identifies patients who can benefit from olaparib beyond mutations in these 5 genes. This hypothesis will be tested in cohort 2.