In addition, none of the abovementioned factors influenced the line of treatment in which first post-CDK4/6i chemotherapy was applied, apart from (1) the time from metastatic disease diagnosis to the end of CDK4/6i therapy (the longer the time, the later the line at which chemotherapy was initiated with a Spearman’s correlation coefficient of 0.34 and p = 0.011), and (2) the type of CDK4/6i applied (the line at which chemotherapy was initiated was significantly later in patients receiving palbociclib than in those receiving ribociclib, p = 0.009). This evidence concerns the gene CDK4 and metastatic neoplasm.