BRCA1 and BRCA2 proteins are critical players in the homologous repair pathway; therefore the use of PARP inhibitors in BRCA-defective cancer cells is thought to lead to genetic damage and cell death by a synthetic lethal effect, which is borne out in clinical trials as PARP-inhibitors have shown more response in patients with BRCA-mutated breast cancers [12], [49]. This evidence concerns the gene BRCA1 and breast cancer.