The efficacy and safety of docetaxel-based chemotherapy combined with dexamethasone 1 mg daily oral administration: JMTO Pca 10-01 phase II trial

Objectives: Previously, one randomized control trial (TAX327) revealed the efficacy of docetaxel-based chemotherapy combined with prednisone. On the other hand, several studies showed a high prostate specific antigen (PSA) response with low-dose dexamethasone in castration-resistant prostate cancer (CRPC) patients. The objective of this study was to evaluate the efficacy and safety of docetaxel-based chemotherapy combined with dexamethasone in CRPC patients.

Materials and methods: This study was a single-arm multi-institutional phase II trial. Patients received 75 mg/m2 of docetaxel, and 0.5 mg of dexamethasone orally twice a day continuing throughout the treatment period. Treatment was planned for 10 cycles, and continued for at least four cycles depending on the observation of PSA flare. The primary endpoint was PSA response defined as a reduction from baseline of at least 50% that continued for at least 3 weeks. Secondary endpoints were safety, PSA flare, time to PSA failure and adherence rate to protocol treatment (10 cycles).

Results: Between January 2011 and February 2014, a total of 76 chemotherapy-naïve CRPC patients were enrolled. Seventy-five patients received docetaxel-based chemotherapy combined with dexamethasone. The median age and PSA level at enrollment were 71 years (53-85) and 23.2 ng/mL (2.9-852), respectively. PSA response rate was 76.8% (90% confidence interval (CI): 66.9-84.9). Of all patients, 30 patients completed 10 cycles of chemotherapy (40%). The incidence rate of PSA flare was 10.7% (eight patients). The median time to PSA failure was 369 days (95% CI: 245-369). The most frequently observed adverse event was hematotoxicity (neutropenia of G2 or greater: 100%).

Conclusions: The present study showed a significantly high PSA response compared with previous reports. Most patients tolerated the protocol treatment well, whereas hematotoxicity was often observed.