Prognostic impact of ESR1 mutations in ER+ HER2- MBC patients prior treated with first line AI and palbociclib: An exploratory analysis of the PADA-1 trial.

1010Background: The question of which is the best endocrine partner to CDK4/6 inhibitors in first line for ER+ HER2- metastatic breast cancer (MBC) remains open. ESR1 mutations might be of paramoun...