Increases in bone turnover marker levels at an early phase after starting zoledronic acid predicts skeletal-related events in patients with prostate cancer with bone metastasis

OBJECTIVE To examine whether bone turnover markers could be predictive markers of the probability of newly arising skeletal-related events (SRE) after the start of zoledronic acid treatment in patients with prostate cancer with bone metastasis. PATIENTS AND METHODS In all, 30 patients with prostate cancer with bone metastasis were treated with zoledronic acid infusion every 4 weeks. Serum C-terminal crosslinking telopeptide of type 1 collagen (1CTP), bone alkaline phosphatase (BAP), and prostate-specific antigen (PSA) levels were measured at the start of zoledronic acid treatment to establish baseline values, and every 4 weeks thereafter. To judge in the early phase whether zoledronic acid is effective in these patients, we retrospectively compared 1CTP, BAP, and PSA levels at 1, 3, and 6 months after starting zoledronic acid treatment with those at baseline. RESULTS SRE-free survival of patients with increases of 1CTP levels at 1 and 3 months and BAP levels at 3 months were significantly poorer than those of patients with decreases in 1CTP or BAP levels (P = 0.001, P = 0.042, and P = 0.004, respectively). Overall survival of patients with increases of 1CTP levels at 1 and 3 months and of BAP levels at 6 months were significantly poorer than those of patients with decreases of 1CTP or BAP levels (P = 0.013, P = 0.027, and P = 0.035, respectively). CONCLUSION The measurement of 1CTP and BAP levels at an early phase after starting zoledronic acid treatment may be useful for physicians to inform patients of their prognosis and to determine the subsequent treatment plan.