Rational indication for docetaxel rechallenge in metastatic castration-resistant prostate cancer

OBJECTIVE To determine whether prostate-specific antigen (PSA) response at first-line chemotherapy with docetaxel correlates with PSA response and survival at docetaxel rechallenge in patients with metastatic castration-resistant prostate cancer (mCRPC). PATIENTS AND METHODS We retrospectively evaluated the oncological outcomes of patients with mCRPC, who were treated with full-dose (75 mg/m(2)), 3-weekly docetaxel plus prednisone/prednisolone at first-line chemotherapy and rechallenge, between 1999 and 2011, at our institution. The endpoints were PSA-progression-free survival (PSA-PFS) and overall survival (OS) at docetaxel rechallenge. Statistical analyses included Kaplan-Meier curves and log-rank tests to evaluate the effect of PSA response at first-line chemotherapy on PSA-PFS and OS at rechallenge. RESULTS Fourty-four patients were included in the analysis. At a median (range) follow-up of 26.4 (9.8-89.8) months after the first administration of docetaxel, 24 (55%) patients had died. At first-line chemotherapy, 36 (82%) patients achieved a reduction in PSA level of >= 50%. At rechallenge, 10 (28%) patients responded with a reduction of >= 50% for a second time. The median (95% confidence interval [CI]) PSA-PFS was 5.9 (95% CI 3.5-6.8) months and the median OS was 21.8 (95% CI 19.9-23.7) months at docetaxel rechallenge. Of the PSA response variables evaluated, only a PSA level reduction of >= 50% at first-line chemotherapy correlated significantly with prolonged PSA-PFS (5.8 vs. 4.5 months; P = 0.01) and OS (22.1 vs. 7.2 months; P = 0.03) at rechallenge. CONCLUSION In the present single-institution study, a reduction in PSA level of >= 50% at first-line chemotherapy with docetaxel correlated with superior PSA-PFS and OS in the rechallenge setting and might, therefore, present a rational indication for docetaxel rechallenge.