A Study of Palbociclib (PD-0332991) + Letrozole vs. Letrozole For 1st Line Treatment Of Postmenopausal Women With ER+/HER2- Advanced Breast Cancer (PALOMA-2)

Inclusion Criteria

• Adult women with locoregionally recurrent or metastatic disease not amenable to curative therapy.
• Confirmed diagnosis of ER positive breast cancer
• No prior systemic anti-cancer therapy for advanced ER+ disease.
• Postmenopausal women
• Measurable disease as per Response Evaluation Criterion in Solid Tumors [RECIST] or bone-only disease
• Eastern Cooperative Oncology Group [ECOG] 0-2
• Adequate organ and marrow function
• Patient must agree to provide tumor tissue

Exclusion Criteria

• Confirmed diagnosis of HER2 positive disease
• Patients with advanced, symptomatic, visceral spread that are at risk of life threatening complication in the short term
• Known uncontrolled or symptomatic CNS metastases
• Prior (neo)adjuvant treatment with letrozole or anastrozole with DFI ≤ 12-months from completion of treatment.
• Prior treatment with any CDK 4/6 inhibitor.