Phase II Trial of Docetaxel With Rapid Androgen Cycling for Progressive Noncastrate Prostate Cancer

Abstract

Purpose We evaluated rapid androgen cycling in combination with docetaxel for men with progressive noncastrate prostate cancers. Patients and Methods Noncastrate patients with ≤ 6 months of hormone therapy were eligible. Cohort 1 (62 patients) received six 28-day cycles of docetaxel (75 mg/m2), leuprolide, and 7 days of topical testosterone. Cohort 2 (38 patients) received nine 21-day cycles of docetaxel (70 mg/m2), leuprolide, and 3 days of testosterone. The primary end point was the proportion of patients at 18 months who achieved noncastrate testosterone levels (> 150 ng/dL) and an undetectable prostate-specific antigen (PSA; ≤ 0.05, ≤ 0.5, or ≤ 2.0 ng/mL with prior prostatectomy, radiation therapy, or no definitive therapy, respectively). Cytochrome P450 3A4 (CYP3A4) activity and docetaxel pharmacokinetics were evaluated. Results A higher proportion of patients achieved the undetectable PSA outcome at 18 months in cohort 2 relative to cohort 1 (13% v 0%). The 16% incidence of febrile neutropenia was higher than that observed in patients was castration-resistant disease, which may have been related to a 50% reduction in overall docetaxel clearance in the noncastrate group. There was no alteration in CYP3A4 activity (P = .87) or docetaxel clearance (P = .88) between cycles. Conclusion The undetectable PSA end point allows for a rapid screening of interventions for further study. Increasing the number of docetaxel cycles after a shorter period of testosterone repletion, and a longer duration of testosterone depletion, increased the proportion of men who achieved an undetectable PSA. The higher-than-expected incidence of febrile neutropenia may have been related to the reduced overall docetaxel clearance in patients with noncastrate versus castrate testosterone levels.