Recent advancements include the combination of endocrine therapy with immunotherapy based on immune checkpoint inhibitors, namely, the cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors (palbociclib, ribociclib, abemaciclib), emerging as the most promising therapeutic strategy for advanced luminal BC patients negative for HER2 expression [22]. This evidence concerns the gene CDK4 and breast cancer.