Correlative biomarker analysis of intrinsic subtypes and efficacy across the MONALEESA phase III studies

A retrospective exploratory analysis of three MONALEESA studies (endocrine therapy plus ribociclib or placebo for HR-positive, HER2-negative advanced breast cancer) evaluated the association of intrinsic subtypes with prognosis and treatment benefit. The intrinsic subtypes were strongly and independently associated with progression-free survival on endocrine-based therapy. Patients with luminal A, luminal B, HER2-enriched, and normal-like subtypes had consistent benefit from addition of ribociclib to endocrine therapy, while patients with basal-like subtype did not benefit from ribociclib.