Given the strong biologic rationale and supporting preclinical data for evaluating CDK4/6 inhibition in patients with oligodendroglioma,8,10,18 a previous phase 2 clinical trial evaluated palbociclib, the first selective CDK4/6 inhibitor to receive FDA approval, in patients with recurrent retinoblastoma-positive anaplastic oligodendroglioma (AO).25 In that study, Sepulveda-Sanchez et al. enrolled 34 patients with AO that had progressed despite prior RT and chemotherapy and who had conserved retinoblastoma protein (pRb) expression in the tumor by immunohistochemistry. Here, RB1 is linked to retinoblastoma.