Cell-Free DNA and RNA in Blood fromMetastatic Prostate Cancer Patients

PRIMARY OBJECTIVES: I. To document the appearance of androgen receptor isoform splice variant 7 (AR-V7) expression over the course of therapy in castration-resistant prostate cancer (CRPC). II. To determine whether detectable AR-V7 is associated with a shortened duration of treatment benefit of abiraterone or enzalutamide. SECONDARY OBJECTIVES: I. To determine how the presence and expression level of AR-V7 impacts response to docetaxel. II. To determine at what point AR-V7 arises during androgen deprivation therapy (ADT) and how its presence and expression corresponds to castration resistance. TERTIARY OBJECTIVES: I. To determine if androgen receptor isoform splice variants (AR-Vs) other than AR-V7 play a role in resistance and / or response to the therapies explored in this study. II. To determine if, in patients who do not express mutations in androgen receptor (AR), other genetic alterations are associated with treatment outcomes to the therapies explored in this study. OUTLINE: Patients undergo blood collection every 4-12 weeks during ADT, abiraterone and / or enzalutamide and docetaxel. Patients switched from ADT to either abiraterone or enzalutamide during the study will undergo phlebotomy every 6-12 weeks. Samples are analyzed for cell-free ribonucleic acid (cfRNA), cell-free deoxyribonucleic acid (cfDNA), AR-V7, and other AR-Vs via quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). After completion of study, patients are followed up for 3 years.