Preclinical studies have indicated that CDK4/6 inhibitors can sensitize breast cancer cells to radiotherapy, possibly by inhibition of DNA damage repair response, enhancement of apoptosis and blockage of cell cycle progression, and inhibition of intra-tumor cellular metabolism and angiogenesis (Han et al., 2013; Pesch et al., 2020; Petroni et al., 2021). Here, CDK4 is linked to breast cancer.