CDK4 and neoplasm: In that analysis, we found that OS was influenced by initial visceral metastasis (hazard ratio:2.20; p = 0.027), number of initial metastatic organs (hazard ratio:1.71, p = 0.048), ER driven tumor (hazard ratio:0.19, p < 0.001), and visceral organ disease progression after a CDK4/6 inhibitor (hazard ratio: 2.64, p = 0.020).