Functional and pharmacodynamic evaluation of metronomic cyclophosphamide and docetaxel regimen in castration-resistant prostate cancer.

AIM: The aim of our study was to investigate the association of docetaxel and metronomic cyclophosphamide (CYC) in castration-resistant prostate cancer (CRPC). MATERIALS & METHODS: CRPC xenografts were established with PC3 cells. Mice were treated with a combination of CYC (50 mg/kg/day) and docetaxel (10-30 mg/kg/week) or with docetaxel alone. Docetaxel plasma levels were analyzed in patients receiving the drug alone or combined with CYC. RESULTS: Metronomic CYC is an effective adjuvant in blocking tumor growth in vivo, with comparable efficacy and less toxic effects compared with docetaxel treatment. CYC acts by downregulating cell proliferation and inducing apoptosis thorough upregulation of p21 and inhibition of angiogenesis. Finally, CYC increases docetaxel plasma levels in patients. CONCLUSION: Metronomic CYC exerts anti-tumoral effects in an in vivo model of prostate cancer and in patients with CRPC, and also increases the bioavailability of docetaxel. These results explain the favorable toxicity and activity profiles observed in patients treated with this regimen.