Aim. This sub analysis of TROPIC study evaluates overall survival (OS) under cabazitaxel in patients who had no initial response to docetaxel (D ) and discontinued D for disease progression and those who initially responded to D but experienced disease progression < 3 months since last D dose. These patients are believed unlikely to benefit from D re-treatment and need new treatment options such as cabazitaxel.

Methods. Of the 755 patients with metastatic castration-resistant prostate cancer (mCRPC) enrolled in TROPIC study, 362 (47.9%) had no initial response to D and discontinued it for disease progression, 155 (20.5%) had an initial response to D therapy according to investigator judgment but progressed < 3 months since last D dose and 238 (31.5%) did not belong to these two subgroups. All patients were randomized to receive cabazitaxel 25 mg/m² or mitoxantrone 12 mg/m² both every 3 weeks and prednisone 10 mg per os daily.

Results. Median OS with cabazitaxel was consistently longer than with mitoxantrone in all subgroups. The highest survival benefit versus mitoxantrone was observed for patients who initially responded to D and then progres­sed < 3 months since last D dose (median OS 15.7 versus 11.6 months, Hazard ratio (HR) 0.52 [95% CI 0.35–0.76]). Median PFS was also significantly improved in the latter subgroup compared to mitoxantrone (2.6 versus 1.4 months, HR 0.66 [0.48–0.91]).

Conclusion. Cabazitaxel plus prednisone consistently shows a greater survival benefit compared to mitoxantrone plus prednisone whatever the subgroup considered, including responders to first-line D who progressed < 3 months since last D and pts without initial response to D who discontinued it for disease progression.