CDKN2A and chordoma: To investigate the efficacy of palbociclib in patients with advanced chordoma, we conducted a multicenter phase II study as part of the National Center for Tumor Diseases (NCT) Precision Medicine in Oncology (PMO) program, NCT PMO-1601 (NCT03110744), which enrolled patients with p16 loss [by immunohistochemistry (IHC)] or CDKN2A loss (by genomic analysis) and CDK4/6 and RB1 presence (by IHC or RNA sequencing).