Weekly versus 3-weekly cabazitaxel for the treatment of castration-resistant prostate cancer: A randomised phase II trial (ConCab)

Aim: Patients treated with cabazitaxel for metastatic castration-resistant prostate cancer (mCRPC) may experience dose delays and reductions or terminate treatment because of toxicity. A lower and more frequent dose of cabazitaxel could improve dose intensity.

Patients and methods: This prospective, multi-center, phase II study randomly assigned 101 patients to Arm A, cabazitaxel Q3W, 25 mg/m² or Arm B, Q1W, 10 mg/m² 5 of 6 weeks. The primary end-point was dose intensity, and we hypothesised that the experimental arm (Arm B) would result in a 20% absolute increase in the relative cumulative dose by week 18. Secondary end-points were overall survival (OS), progression-free survival (PFS), pain progression, radiological and prostate-specific antigen (PSA) response rates, quality of life (Functional Assessment of Cancer Therapy Prostate) and tolerability.

Results: Median doses of cabazitaxel were 276 mg (45-320) and 257 mg (20-330) in Arms A and B, respectively, at week 18 (p = 0.13). More patients in Arm B stopped treatment because of toxicity. Median PFS in Arms A and B were 6.0 and 6.4 months (hazard ratio [HR] 0.73, 95% confidence interval [CI]: 0.47-1.13, p = 0.156) and for OS, 14.6 and 15.6 months (HR 0.95, CI: 0.58-1.58, p = 0.85), respectively. PSA responses ≥50% were seen in 52% and 46% of patients in Arms A and B, respectively. A higher incidence of febrile neutropenia was observed in the standard arm (10 events versus 1, p < 0.008). A grade V febrile neutropenia occurred in Arm A. Low-grade haematuria was more prevalent with weekly cabazitaxel (15 events versus 5, p = 0.003). Three patients in Arm B experienced clinically significant inflammation of the ureters. A toxicity is not previously described for cabazitaxel.

Conclusion: Weekly cabazitaxel reduces the incidence of febrile neutropenia but does not increase the dose intensity compared with the standard therapy. Cabazitaxel has clinical meaningful efficacy in heavily pre-treated patients with mCRPC.