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

Inclusion Criteria:

A patient will be eligible for androgen receptor expression testing (STEP 1) if the following criteria are met:

* Female
* Pathologically confirmed invasive cancer of the breast
* ER/PR status (ER or PR defined as positive if ≥1%; ER/PR is defined as negative if \<1%):
* Phase I: Patients may have ER/PR(-) breast cancer.
* HER2 normal (IHC 0-1; FISH \< 2.0)
* Non-measurable or measurable, metastatic disease
* Available tissue for AR testing for research purposes

A patient will be eligible for participation in the therapeutic trial (STEP 2) if the following criteria are met:

* Androgen receptor expression testing confirms that the patient's tumor is AR (+). AR is considered positive if ≥1% of cell nuclei are immunoreactive using the Dako antibody (clone AR441). Receptor testing may be performed on either primary tumor specimen or tissue from a metastatic site. Local testing permitted for eligibility but will require confirmation at MSKCC.
* There is no limit to the number of prior chemotherapy or endocrine therapy regimens allowed. Patients with ER(+) AR(+) breast cancer must have had at least 1 prior line of endocrine therapy to be eligible for the phase I portion of the trial.
* At least 2 weeks since last cytotoxic chemotherapy, hormonal therapy, or radiotherapy. Toxicities related to prior therapy must either have returned to grade 1, or baseline (excluding alopecia)
* Patient may receive bisphosphonates/denosumab for the palliation of bone metastases
* If patient has a history of brain metastases or leptomeningeal disease, lesions must be stable for at least 3 months (as documented by either head CT or brain MRI)
* Prior treatment with bicalutamide will not be allowed
* At least 3 weeks from major surgery with full recovery
* ECOG performance status 0-2
* Age 18 years or greater
* Postmenopausal. Use of LHRH agonist permitted.
* Patients must not have another, non-breast, active malignancy that requires treatment.
* The effects of palbociclib on the developing human fetus at the recommended therapeutic dose are unknown. Women of child-bearing potential must agree to use adequate contraception (barrier method of birth control; abstinence). Women must not breast feed while on study.
* Ability to understand and the willingness to sign a written informed consent document.
* Ability to swallow intact palbociclib capsules and bicalutamide tablets.
* Adequate organ and marrow function as defined below (ULN indicates institutional upper limit of normal):

  * Absolute neutrophil count ≥ 1.5 10\^9/
  * Hemoglobin ≥ 9.0 g/dL
  * WBC ≥ 3.0 10\^9/L
  * Platelets ≥ 100 10\^9/L
  * Total bilirubin ≤ 1.5 ULN except for patients with known Gilbert syndrome
  * AST(SGOT)/ALT(SGPT) ≤ 3 institutional ULN
  * Plasma creatinine ≤ 1.5 ULN or Creatinine Clearance \> 50 mL/min (calculated by Cockcroft-Gault method)
  * QTc interval ≤ 470 msec

Exclusion Criteria:

* Patients who have not recovered from adverse events of prior therapy to ≤ NCI CTCAEv4.0 Grade 1.
* Patients receiving any other investigational anti-cancer agents.
* Patients who have received prior treatment with a selective CDK4/6 inhibitor
* Patients who have received prior anti-androgen therapy
* History of allergic reactions attributed to compounds of similar chemical or biologic composition to palbociclib.
* Uncontrolled intercurrent illness including, but not limited to, known ongoing or active infection, including HIV, active hepatitis B or C, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia (specifically, uncontrolled atrial fibrillation or ventricular dysrhythmias except ventricular premature contractions), or psychiatric illness/social situations that would limit compliance with study requirements.
* Pregnant women and women who are breast-feeding.
* Patients with a history of long-QT syndrome or documented family history of long-QT syndrome. Patients who must remain on drugs that prolong the QT interval.
* Palbociclib is a substrate of CYP3A. Caution should be exercised when dosing palbociclib concurrently with CYP3A inducers or inhibitors. Furthermore, patients who are taking concurrent medications that are strong inducers/inhibitors or substrates of CYP3A4 should be switched to alternative medications to minimize any potential risk.