Continuous versus Standard Palbociclib Treatment and Molecular Profiling of Solid Tissues and Liquid Biopsies in the CCTG MA.38 Trial in Advanced Breast Cancer

A continuous 100 mg dosing schedule of palbociclib was tolerable but not associated with improved efficacy signals versus the standard intermittent 125 mg (days 1-21 of a 28-day cycle) schedule. Mutations detected in liquid biopsies and changes in cfDNA dynamics were linked to poor outcomes and may identify patients with treatment-resistant cancer.