CDK4 and breast cancer: Our preferred treatment is in accordance with current guideline recommendations from the National Comprehensive Cancer Network® (NCCN®), European Society for Medical Oncology (ESMO), and the 5th European School of Oncology (ESO)-ESMO international consensus guidelines for advanced breast cancer (ABC 5): CDK4/6i + AI or CDK4/6i + fulvestrant are preferred first-line therapies.