As a result, patients with mutated BRCA1/BRCA2 are suitable candidates for additional treatment with PARP inhibitors, such as the recently approved drug olaparib which was approved in 2019 in Europe for germline BRCA1/2-mutated HER2− breast cancer (Griguolo et al., 2018; Le and Gelmon, 2018). Here, BRCA1 is linked to breast cancer.