CDK4 and breast cancer: However, they exhibited lower median PFS, which may reflect the intrinsic aggressiveness of BRCA1/2-mutated breast cancer.34,54 Additionally, none of these patients received a poly (ADP-ribose) polymerase inhibitor and only 2 received carboplatin-based CT as post-CDK4/6i treatment.35,55 These findings should be interpreted with caution due to the small number of BRCA1/2 pathogenic variant carriers (n = 16) and the variability in treatment received.