The role of Cabazitaxel in Patients With Castration-Resistant and Osseous Metastases Prostate Cancer. A Hellenic Cooperative Oncology Group Phase II Study: Cabazitaxel in mCRPC patients with osseous metastases.

Background: Cabazitaxel is an effective treatment in metastatic castration-resistant prostate cancer (mCRPC) patients previously exposed to docetaxel and novel hormonal treatments. Understanding the molecular biology of mCRPC disease and taking into account the several approved treatment options, biomarkers are needed to guide decision making including cabazitaxel treatment.

Methods: Cababone was a phase II translational study that attempted to identify predictors of cabazitaxel efficacy. mCRPC with documented bone metastases were enrolled prospectively and treated with cabazitaxel 25mg/m every 3 weeks. Prostate cancer biopsies, bone marrow aspirates and blood samples were collected for translational research.

Results: Sixty patients were enrolled and 59 received treatment according to protocol. Six-month progression free survival (PFS) rate was 47% (95% CI: 33% - 59%) and 12-month Overall Survival (OS) rate was 70% (95% CI: 56% - 80%). Patients with reactive hematopoiesis had improved PFS and OS with cabazitaxel treatment. Mutations in HRR genes were detected in 7 patients.

Conclusions: No differences in cabazitaxel efficacy were noted according to mutational status of HRR genes analyzed. No new safety issues were detected. In conclusion, CabaBone confirmed efficacy of cabazitaxel in mCRPC patients including the subgroup of patients with HRR mutations. Reactive hematopoiesis in bone marrow biopsies was related to improved survival warranting further investigation of bone biomarkers as predictors of cabazitaxel efficacy.