Palbociclib in Combination With Bicalutamide for the Treatment of AR(+) Metastatic Breast Cancer (MBC)

The study therapy is to be self administered on an outpatient basis. Patients who meet eligibility criteria and sign informed consent to Step 2 may begin treatment on study. Treatment consists of bicalutamide orally once daily and palbociclib will be given orally daily for 3 weeks on followed by 1 week off. A treatment cycle is considered to be 4 weeks. Eligible patients will be evaluated for toxicity every 2 weeks during Cycle #1 and 2, followed by every 4 weeks in subsequent cycles. Toxicity assessment will include history, physical examination including vital signs, and laboratories including complete blood count and comprehensive metabolic panel. Patients will keep a drug diary to document adherence to oral therapy. Radiographic response evaluation per RECIST will occur every 8 weeks (2 cycles) for cycles 1-6 and then every 12 weeks thereafter with high-resolution CT scan. Patients with suspected bone-only lesions must have bone lesions assessed by CT with bone windows or by bone scan at screening. Phase I: We will use a standard 3+3 design for the dose finding lead in to establish the recommended phase II doses for the combination of palbociclib and bicalutamide. The doses for Phase I will be determined based on the dose level to which the patient is accrued. Phase II: Treatment consists of bicalutamide orally once daily and palbociclib will be given orally daily for 3 weeks on followed by 1 week off at the doses determined in phase I.