A Prospective, Open Label, Randomized Phase II Trial of Weekly Docetaxel Versus Weekly Vinorelbine as First Line Chemotherapy in Patients With Androgen Independent Prostate Cancer

Purpose

In previous phase I to III studies docetaxel and vinorelbine have shown promising activity in androgen independent prostate cancer. In the present trial we assessed the efficacy and tolerability of single agent low dose docetaxel vs vinorelbine in patients with advanced androgen independent prostate cancer.

Materials and Methods

A total of 40 chemotherapy naive patients with histologically proven androgen independent prostate cancer, adequate androgen ablation, and clinical and/or biochemical progression were randomly assigned to receive either 25 mg/m² docetaxel (arm A) or 25 mg/m² vinorelbine (arm B) weekly. Treatment was continued until clinical and/or biochemical progression. In cases of progression patients switched to the alternative treatment arm. The primary end point was time to disease progression. Secondary end points included prostate specific antigen response rates in sequential treatment, analgesic response and toxicity.

Results

The current analysis showed a doubled risk of progression in treatment arm B. The median time to first disease progression was 14.5 months for arm A vs 4.4 months for arm B. The proportion of patients with a greater than 50% prostate specific antigen decrease on first line therapy was significantly higher in arm A (62.5%) compared to arm B (11.1%) (p = 0.0033). After progression to docetaxel second line vinorelbine yielded a greater than 50% prostate specific antigen response rate of 28.6% vs 62.5% for second line docetaxel. Clinically significant toxicity occurred more often in arm B with neutropenia grade 4 seen in 22% and grade 3 in 28% of patients (p = 0.0005) during the first treatment phase.

Conclusions

While weekly application of both cytotoxic agents was well tolerated, this study demonstrates the superiority of docetaxel vs vinorelbine as monotherapy in the treatment of androgen independent prostate cancer.

Key Words: prostatic neoplasms, drug therapy, docetaxel, vinorelbine

Abbreviations and Acronyms: AIPC, androgen independent prostate cancer, CT, computerized tomography, EMP, estramustine phosphate, PSA, prostate specific antigen, TTP, time to progression