Study Of Letrozole With Or Without Palbociclib (PD-0332991) For The First-Line Treatment Of Hormone-Receptor Positive Advanced Breast Cancer

Inclusion Criteria

• Inoperable estrogen receptor positive and HER2 negative breast cancer.
• Postmenopausal status.
• Tumor tissue (archived acceptable) available for biomarker studies. For Phase 2 Part 2 - CCND1 amplification and/or loss of p16 as determined by the central laboratory.
• Acceptable bone marrow, liver and kidney function.

Exclusion Criteria

• Prior or concomitant treatment for advanced breast cancer.
• Other major cancer in the past 3 years.
• Important cardiovascular events in the past 6 months.