BRCA1 and ovarian serous carcinoma: Olaparib treatment has been most successful in minimizing tumor growth and delaying tumor recurrence in high-grade serous ovarian carcinoma (HGSOC) [5,6], the most common and most lethal subtype of ovarian cancer, where 50% of cases are estimated to be HR-deficient primarily through genomic inactivation of BRCA1/2 [7,8].