Cabazitaxel Shows Efficacy in Metastatic Castration-Resistant Prostate Cancer with Osseous Metastases

Key Insights

• A Phase II study (CabaBone) confirms cabazitaxel's efficacy in metastatic castration-resistant prostate cancer (mCRPC) patients, including those with HRR mutations, previously treated with docetaxel.
• The study found a 6-month progression-free survival rate of 47% and a 12-month overall survival rate of 70% in mCRPC patients with bone metastases treated with cabazitaxel.
• Reactive hematopoiesis in bone marrow biopsies was associated with improved survival, suggesting bone biomarkers could predict cabazitaxel efficacy in mCRPC patients.

Cabazitaxel remains an effective treatment option for patients with metastatic castration-resistant prostate cancer (mCRPC) who have previously been treated with docetaxel and novel hormonal therapies, according to a recent phase II study. The CabaBone trial, a Hellenic Cooperative Oncology Group study, prospectively enrolled mCRPC patients with documented bone metastases to identify predictors of cabazitaxel efficacy.

Study Design and Results

The study enrolled sixty patients, with fifty-nine receiving cabazitaxel at a dose of 25mg/m2 every three weeks. The primary objective was to assess the six-month progression-free survival (PFS) rate, which was found to be 47% (95% CI: 33% - 59%). The twelve-month overall survival (OS) rate was 70% (95% CI: 56% - 80%). Translational research included prostate cancer biopsies, bone marrow aspirates, and blood samples to identify potential biomarkers.

Biomarker Analysis

Interestingly, patients exhibiting reactive hematopoiesis showed improved PFS and OS with cabazitaxel treatment. Mutations in HRR genes were detected in seven patients; however, no significant differences in cabazitaxel efficacy were observed based on the mutational status of the HRR genes analyzed. These findings suggest that reactive hematopoiesis in bone marrow may serve as a predictive biomarker for cabazitaxel response, warranting further investigation.

Safety Profile

The study reported no new safety concerns associated with cabazitaxel, reinforcing its established safety profile in mCRPC patients.

Clinical Implications

"CabaBone confirmed efficacy of cabazitaxel in mCRPC patients including the subgroup of patients with HRR mutations," the researchers noted. The results highlight the potential of bone marrow biomarkers, specifically reactive hematopoiesis, in predicting treatment response and guiding clinical decision-making for cabazitaxel use in mCRPC patients with osseous metastases. Further research is needed to validate these findings and explore the underlying mechanisms linking reactive hematopoiesis to cabazitaxel efficacy.