CDK4 and leiomyosarcoma: Given that the phase II trial of the CDK4/6 inhibitor palbociclib in advanced sarcoma, which selected patients based onCDK4 mRNA expression relative to CDKN2A, achieved its primary endpoint (52), and the successful combination of ribociclib (CDK4/6 inhibitor) with everolimus (mTOR inhibitor) in advanced dedifferentiated liposarcoma and leiomyosarcoma (53), other CDK4/6 inhibitors warrant further investigation in IS.