CDK4 and breast cancer: In terms of clinical data, the CDK4/6 inhibitor palbociclib did not appear to significantly affect estradiol and FSH levels in patients affected by breast cancer (Furlanetto et al., 2022), while no data are available with the two approved CDK4/6 inhibitors, abemaciclib and ribociclib, in the adjuvant setting, (Scavone et al., 2023).