Efficacy of combined androgen blockade with zoledronic acid treatment in prostate cancer with bone metastasis: the ZABTON-PC (zoledronic acid/androgen blockade trial on prostate cancer) study

Zoledronic acid (ZA) reduces the risk of skeletal-related events (SREs) in castration-resistant prostate cancer (CRPC) with bone metastasis and improves quality of life. It remains unclear when clinicians should initiate ZA treatment. Hormone-naïve patients were randomized to a combined androgen blockade (CAB) group or CAB with ZA group (CAB-ZA) based on Gleason score (GS) or extent of disease. The primary end-point of the study was progression-free survival (PFS) and the secondary end-point was incidence of SREs and bone pain. Thirty-one and 29 patients among 60 enrolled patients were assigned to the CAB group and the CAB-ZA group, respectively. There was no significant difference in PFS between the two groups. Subgroup analyses revealed better PFS in the CAB-ZA group with GS ≥8 (p=0.021). Moreover, incidence of SREs, including bone pain, was lower in the CAB-ZA group (p=0.019). CAB-ZA treatment was found to improve PFS for patients with prostate cancer with high GS. CAB-ZA treatment could be recommended for treatment of patients with prostate cancer.