Outcome, clinical prognostic factors and genetic predictors of adverse reactions of intermittent combination chemotherapy with docetaxel, estramustine phosphate and carboplatin for castration-resistant prostate cancer
Docetaxel-based chemotherapy is effective in patients with castration-resistant prostate cancer (CRPC). This phase II study assessed the outcome and predictive factors for prognosis and toxicity following intermittent chemotherapy with docetaxel, estramustine phosphate, and carboplatin (DEC) in patients with CRPC. Thirty-five patients were treated with a DEC regimen that consisted of a 28-day cycle of drugs as follows: docetaxel (60 mg/m2 on day 1), carboplatin (AUC 5 on day 1) and estramustine phosphate (560 mg daily). Treatment was continued intermittently. The end point was to test the effect of DEC on the response rate and overall survival (OS). Statistical correlations between the outcomes and predictive factors, including clinical parameters and 8 single-nucleotide polymorphisms (SNPs) related to drug metabolism, were assessed. Prostate-specific antigen levels decreased by more than 30% in 65.7% of the patients. The median OS following DEC was 17.8 months, and the median total time of chemotherapy holiday was 7.7 months (range 1.7–35.8). On multivariate analysis, serum lactate dehydrogenase (LDH) was an independent prognostic factor for OS (p = 0.007). On SNP analysis, patients carrying the TT genotype of the ABCB1 C3435T polymorphism showed a significantly more severe leukocytopenia during the first cycle of DEC therapy compared to patients with the CC + CT genotype (p = 0.036). Combination chemotherapy with DEC has a potential effect on CRPC with acceptable toxicity. Serum LDH may be a promising predictor of prognosis, and the ABCB1 C3435T polymorphism may be a genetic predictor of the severity of leukocytopenia in patients with CRPC treated with DEC.