Effectiveness of taxanes-based chemotherapy against hormone-refractory prostate carcinoma

We performed an investigative and clinical study of docetaxel, and evaluated its efficacy against hormone-refractory prostate carcinoma (HRPC). In an in vitro experiment, docetaxel suppressed the human prostate cell line proliferation not only in an androgen-dependent cell line, LNCaP, but also in androgen-independent cell line, PC-3, in a dose-dependent manner. In an in vivo experiment applying an SCID mouse xenograft model with PC-3, docetaxel administration suppressed the tumor growth more than 95%. In a clinical study, eight cases were enrolled to low-dose (20 mg/m ²/wk) weekly regimen and an other eight to high-dose (60 mg/m ²/wk) administration of docetaxel every three weeks. A prostate specific antigen (PSA) decline of more than 50% were observed in 4 (50%) in the low-dose group and 5 (63%) in the high-dose group. The median time to progression and overall survival were 8.5 and 13.2 months in the low-dose group and more than 5.5 and 8.5 months in the high-dose one, respectively. This regimen was well tolerated, and the incidence of adverse effect was relatively low and light. Grade 3 neutropenia or leukocytopenia without fever was seen in three patients (18.8%). Only one patient required administration of granulocyte-colony stimulating factor because of neutropenia. No other grade 3 or 4 toxicity was observed. In conclusion, docetaxel-based chemotherapy was well tolerated and an active treatment for HRPC cases.