The CKD 4/6 inhibitor in combination with an endocrine agent has been shown to significantly prolong progression-free survival as compared with the endocrine agent alone in advanced breast cancer [24–26], and this effect was reported to be independent of the degree of endocrine resistance, hormone-receptor expression level, and PIK3CA mutational status [26]. This evidence concerns the gene NR4A1 and breast carcinoma.