9. Absence of significant radiological progression to abiraterone plus prednisone at study entry. Only those cases with limited progression will be eligible if: a) they have not developed any new visceral, nodal or other soft tissue metastases; b) their measurable target lesions on abiraterone plus prednisone according to RECIST 1.1 should have not increased more than 40% from baseline or from their best response on treatment measurements; and c) they must have < 3 new bone metastasis on bone-scan from baseline according to PCWG2