Palbociclib in Patients With Metastatic Castration-Resistant Prostate Cancer

Inclusion Criteria: * Patients must have histologically confirmed adenocarcinoma of the prostate without evidence of small cell/neuroendocrine differentiation. * Patients must consent to blood collection for testing prior to enrollment by a central reference laboratory. Screening will be done through the CRPC Master Screening Protocol (IND234) * Patients must have clinically and/or radiologically documented disease. Patients with elevated PSA only are not eligible. All radiology studies must be performed within 28 days prior to enrollment (within 35 days if negative). * All patients must have consented to the release of a tumour block from their primary or metastatic tumour. The centre/pathologist must have agreed to the submission of the specimen. * Patients must have evidence of either biochemical or radiological disease progression in the setting of surgical or medical castration: * PSA progression: * Minimum of two rising PSA values from a baseline measurement with an interval of ≥ 1 week between each measurement * PSA must be ≥2.0 ug/L * Objective progression: * RECIST 1.1 or * Soft tissue or visceral disease progression or * PCWG3 for bone progression (\>2 new lesions on bone scan or CT) * Surgical/medical castration: * Prior orchiectomy or * LHRH agonist/antagonist and testosterone \< 50 ng/dL or \< 1.7 nmol/L. LHRH agonist/antagonist therapy must be maintained for the duration of study therapy and if previously discontinued, must…