Importantly, within HRD, germline mutations in BRCA1 and BRCA2 genes (which are the best characterised cause of HRD) have been associated with response to the PARP inhibitor olaparib in a phase III clinical trial (POLO) conducted in metastatic, platinum-sensitive, PC patients (first line setting).61 The gene discussed is BRCA1; the disease is pachyonychia congenita.