Does a dose of 20 or 25 mg/m2 of cabazitaxel benefit patients with castration-resistant prostate cancer?

This study aimed to assess the effectiveness and safety of two doses of cabazitaxel  (Jevtana) (20 or 25 mg/m²) in the treatment of castration-resistant prostate cancer (CRPC) in the real-world practice. The study found that a lower dose of cabazitaxel benefited patients at high risk of having side effects whereas the higher dose can be administered to fit patients.  

CRPC is prostate cancer (PC) that no longer responds to androgen deprivation therapy (ADT). ADT is a hormonal treatment that decreases male hormones such as testosterone that helps PC growth. CRPC commonly requires additional therapy such as chemotherapy.  Several new treatments have been introduced for CRPC such as cabazitaxel. 

Cabazitaxel is a chemotherapy drug used in the treatment of CRPC. The standard starting dose of cabazitaxel is 25mg/m². However, some studies suggested that beginning treatment with 20mg/m² would result in fewer side effects. Patients in clinical trials are usually carefully selected and are usually fit. In real-world medical practice, many patients may be older and may have additional medical conditions that would increase their risk for side effects. It is important to determine the real-world safety of cabazitaxel and the most appropriate starting dose in patients with CRPC.

There were 349 patients with CRPC in this trial. 190 patients received cabazitaxel 20mg/m² (C20 group) 159 patients received cabazitaxel 25mg/m² (C25 group). Prostate-specific antigen (PSA) is a protein produced by the prostate. It is usually elevated in PC and can be a marker of relapse. A reduction in PSA means a response to treatment.

The rate of overall side effects was significantly higher in the C25 group (89.3%) compared to the C20 group (78.4%). Also, the rate of serious side effects was significantly higher in the C25 group (81.1% vs. 61.1%). Side effects more common in the C25 group included low white blood cell counts with and without fever.

A PSA response was considered a reduction in PSA levels by 30% or more. The PSA response rate was slightly lower in the C20 group (26.4%) compared to the C25 group (32.0%). The overall survival (OS) rate was 29% longer in the C25 group when compared to the C20 group. 

The authors concluded that survival was higher in the C25 group. They suggested that patients at risk of developing side effects could be started on the C20 dose and prevention of low white blood cell counts may be considered in these patients. 

This study was carried out on a Japanese group of patients with CRPC which may not translate to a larger population. This study was funded by Sanofi, the manufacturer of cabazitaxel.