A Study of Palbociclib (PD-0332991) Plus Letrozole Versus Placebo Plus Letrozole For 1st Line Treatment of Postmenopausal Asian Women With ER (+), HER2 (-) Advanced Breast Cancer (PALOMA-4)

A Multicenter, Randomized, Double-Blind Phase 3 Study of Palbociclib (Oral CDK 4/6 Inhibitor) Plus Letrozole Versus Placebo Plus Letrozole for the Treatment of Previously Untreated Asian Postmenopausal Women With ER (+), HER2 (-) Advanced Breast Cancer