Prediction of favorable outcome in a docetaxel rechallenge setting in metastatic castration-resistant prostate cancer.

Abstract

68 Background: To identify predictors of favourable oncological outcome in metastatic castration-resistant prostate cancer (mCRPC) patients who are treated with docetaxel rechallenge following first-line chemotherapy with docetaxel. Methods: We retrospectively evaluated the oncological outcome of mCRPC patients who were treated with 3-weekly docetaxel (75mg/m2) at first-line chemotherapy and rechallenge plus prednisone/ prednisolone. The endpoints of oncological outcome were PSA-progression-free survival (PSA-PFS) and overall survival (OS) after initiation of docetaxel rechallenge. The effect of clinical variables on PSA-PFS and OS was statistically analysed by a log-rank test or Cox regression with hazard ratios. All analyses were performed using a 0.05 level of significance. Results: 47 patients were included on analysis. At a median follow-up of 25.8 months (range 9.8-89.8 months) after the first administration of docetaxel, 27 (57.4%) patients had died. Median PSA-PFS was 5.9 months (95% CI 3.5-6.8 months) and median OS was 21.4 months (95% CI 18.9-23.9 months) after initiation of docetaxel rechallenge. PSA-reduction ≥ 30% was the only pre-treatment variable that correlated significantly with prolonged PSA-PFS (p=0.03) and OS (p=0.002). Patients with PSA-reduction ≥ 30% at first-line chemotherapy showed a median OS of 21.8 months since initiation of docetaxel rechallenge in comparison to 4.5 months in patients with < 30% PSA-reduction. Conclusions: Docetaxel rechallenge represents an active treatment option in selected docetaxel-pretreated patients with mCRPC. In this retrospective study, PSA-reduction ≥ 30% at first-line chemotherapy with docetaxel predicted superior PSA-PFS and OS in the rechallenge setting and might, therefore, present a rational indication for docetaxel rechallenge.