PARP1 and breast cancer: Notwithstanding, it has taken more than 15 years since the concept of synthetic lethality was first indicated for cancer therapies [2] to develop these PARP inhibitors, which are used to treat breast cancer and high-grade serous ovarian cancer patients with homologous recombination deficiency (HRD), which includes mutation in BRCA1/2, RAD51C/D, or PALB2, hyper-methylation of the BRCA1 promoter, or a series of yet to be defined causes [4].