Trial of Rad-223 Activity in Asymptomatic Patients With mCRPC While on Abiraterone or Enzalutamide Besides AR-V7 Status

Primary objective: To assess the efficacy of radium-223 in asymptomatic patients with mCRPC who have progressed while on abiraterone acetate or enzalutamide treatment. Primary endpoint: To determine the efficacy of radium-223 in terms of radiological rPFS. Secondary objectives: * Safety profile. * To determine the association between AR-V7 status (positive vs. negative) and PFS. * To establish the relationship between CTCs number with radium-223 efficacy. Secondary endpoints: Safety AEs will be evaluated using the Common Terminology Criteria for Adverse Events (CTCAE) of the US National Cancer Institute (NCI) version 4.0 \[20\]. Grade 3 or 4 AEs and serious adverse events (SAEs) will be assessed to determine the safety and tolerability of the various combinations of drugs. Efficacy * Radiographic progression-free survival (rPFS) depending on AR-V7 status. * Overall survival (OS). * Time to first symptomatic skeletal event (SSE). * Time to prostate specific antigen (PSA) progression according to the Alpharadin in Symptomatic Prostate Cancer (ALSYMPCA) study criteria. * Determination percentage of PSA progression. * Alkaline phosphatase level response (AF), normalization of alkaline phosphatase level, according to the ALSYMPCA study criteria. Molecular aspects * Assessment of AR-V7 mutation evolution during the study treatment. * Determination changes in CTCs number during the study treatment.