 4. Metastatic castration-resistant disease with only bone metastases, confirmed by bone scan within 4 weeks or CT within 6 weeks, of starting this trial Cycle 1 Day 1. Patients with local recurrence, and bone metastases with an associated soft tissue component, will be allowed into the trial. Pelvic lymphadenopathy 1.5cm in short axis is not an exclusion. 