CDK4 and breast cancer: In retrospective real-world data with a total of 217 individuals including 15 patients with BRCA1/2 (n = 10), ATM (n = 4), and CHEK2 (n = 1) GPVs, BRCA1/2-ATM-CHEK2 GPVs were suggested to be associated with poor outcomes in advanced BC treated with CDK4/6 inhibitors; however, there were no randomized controlled trials for CDK4/6 inhibitors in patients with GPVs in the HR genes [83].