Docetaxel rechallenge after an initial good response in patients with metastatic castration-resistant prostate cancer

Objective To evaluate the benefit of docetaxel rechallenge in patients with metastatic castration-resistant prostate cancer (mCRPC) relapsing after an initial good response to first-line docetaxel. Patients and Methods We retrospectively reviewed the records of consecutive patients with mCRPC with a good response to first-line docetaxel [serum prostate specific antigen (PSA) decrease >= 50%; no clinical/radiological progression]. We analysed the impact of management at relapse (docetaxel rechallenge or non-taxane-based therapy) on PSA response, symptomatic response (performance status/pain/analgesic consumption), and overall survival (OS). We used multivariate stepwise logistic regression to analyse potential predictors of a favourable outcome. Result We identified 270 good responders to first-line docetaxel. The median progression-free interval (PFI) was 6 months from the last docetaxel dose. At relapse, 223 patients were rechallenged with docetaxel (82.5%) and 47 received non-taxane-based therapy. There was no significant difference in median OS {18.2 [95% confidence interval (CI) 16.1-22.00] and 16.8 [95% CI 13.4-21.5] months, respectively, P = 0.35}. However, good PSA response and symptom relief/stable disease were more frequent on docetaxel rechallenge (40.4% vs 10.6%, P < 0.001 for PSA). A PFI of > 6 months and added estramustine predicted a good PSA response and symptomatic response on docetaxel rechallenge but only a PFI of > 6 months predicted longer OS. Haemoglobin (< 13 g/dL) and pain were associated with reduced OS. Docetaxel rechallenge increased the incidence of grade >= 3 sensory neuropathy, nail disorders and asthenia/fatigue. Conclusions Docetaxel rechallenge is a management option for responders to docetaxel with a PFI of > 6 months, but did not prolong survival. Potential benefits should be weighed against the risk of cumulative toxicity.