High-dose calcitriol, docetaxel and zoledronic acid in patients with castration-resistant prostate cancer: a phase II study

Abstract

Introduction: Docetaxel has become the standard chemotherapy for patients with castration-resistant prostate cancer (CRPC). We wanted to assess the efficacy and safety of a weekly high-dose calcitriol, docetaxel and zoledronic acid combination in CRPC.

Patients and methods: Thirty patients were enrolled to receive calcitriol 0.5 µg/kg orally in 4 divided doses over 4 h on day 1 of each treatment week, docetaxel 36 mg/m(2) i.v. infusion on day 2 of each treatment week and zoledronic acid 4 mg i.v. on day 2 of the first and fifth week of each cycle. Treatment was administered weekly for 6 consecutive weeks on an 8-week cycle.

Results: Out of 23 evaluable patients, there was a response of prostate-specific antigen (PSA) in 11 patients (47.8%); 6 (26.1%) had a stable PSA level for a median of 4.2 months. The median survival time was 15 months (95% confidence interval 13.9-16.1 months). The regimen was generally tolerated; anemia was the only grade 3/4 hematological toxicity in 2 patients.

Conclusions: This regimen was tolerated, and half of the patients had a PSA response. Although our response rates are inferior to some studies using docetaxel, we believe our response rates are acceptable knowing that we are treating CRPC, which still has variable outcomes.