Randomised phase II/III study of docetaxel with or without risedronate in patients with metastatic Castration Resistant Prostate Cancer (CRPC), the Netherlands Prostate Study (NePro)

4518 Background: Bisphosphonates, including risedronate (R), an oral third generation pyridinyl bisphosphonate, exert antitumor activity in vitro and in vivo. Animal models have shown synergistic activity of bisphosphonates and taxanes. This study aimed to investigate the potential benefit of adding R to docetaxel based chemotherapy in patients with metastatic CRPC. Methods: CRPC patients with bone metastasis, and no prior bisphosphonate use were randomly assigned to receive docetaxel (D) 75 mg/m² every 3 weeks and prednisone 5 mg bid as first line chemotherapy, with or without R 30 mg oral od. Upon progression patients in the D alone arm were offered R. The study was designed as a randomized open label phase II, with extension into a phase III study. The primary endpoint was time to progression (TTP). A composite endpoint of objective progression by RECIST criteria, PSA progression, or pain progression, whichever occurred first, was applied. Secondary endpoints were 50% PSA response rate, pain response, ...