Genetic and Molecular Mechanisms in Assessing Response in Patients With Prostate Cancer Receiving Enzalutamide Therapy

Inclusion Criteria: * Histologically or cytologically confirmed adenocarcinoma of the prostate without pure small cell carcinoma; patients without histologically confirmed adenocarcinoma may be eligible if both the treating physician and the study principal investigator (PI) agree that the patient's history is unambiguously indicative of advanced adenocarcinoma * Ongoing androgen deprivation therapy with a gonadotropin-releasing hormone (GnRH) analogue or orchiectomy (i.e., surgical or medical castration); patients who have not had an orchiectomy must maintain effective GnRH-analogue therapy for the duration of the trial * Radiographic evidence of regional or distant metastases with suspected tumor in an area that is safe to biopsy * Willingness to undergo a tumor biopsy at baseline and at disease progression * Serum testosterone level \< 50 ng/dL at screening * Progressive disease by PSA or imaging in the setting of medical or surgical castration; disease progression for study entry is defined as one or more of the following three criteria: * PSA evidence for progressive prostate cancer which consists of a PSA level of at least 2 ng/ml which has risen on at least 2 successive occasions, at least 1 week apart; if the confirmatory PSA value is less than the screening value, then an additional PSA value greater than #2 will be required to document progression of \>= 1 week * PSA values to be obtained \>= 1 week apart * Soft tissue disease progression defined by Respo…