BRCA1 and cancer: Germline BRCA1/2 mutations are well‐established predictive biomarkers of PARPi sensitivity,3, 4, 49 and predict sensitivity to PARPi monotherapy in metastatic breast10, 50 and ovarian17, 51, 52 cancer, and to PARPi maintenance therapy in metastatic ovarian15, 18 and pancreatic14 cancer.