Normalization of bone markers is associated with improved survival in patients with bone metastases from solid tumors and elevated bone resorption receiving zoledronic acid

BACKGROUND. For patients with bone metastases, high N-telopeptide of type I collagen (NTX) levels correlate with increased risks of skeletal-related events and death. However, the relation between NTX decreases and clinical benefits is unclear. METHODS. Correlations between NTX normalization during treatment and clinical outcome were retrospectively analyzed in 3 large, phase 3 trials. Urinary NTX levels were measured at baseline and at Month 3 in patients with bone metastases from breast cancer (BC; n = 578), hormone-refractory prostate cancer (HRPC; n = 472), or nonsmall-cell lung cancer and other solid tumors (NSCLC/OST; n = 291) who received zoledronic acid or control (pamidronate for BC; placebo for HRPC and NSCLC/OST) for up to 24 months. NTX levels were characterized as normal (N; <64 nmol/mmol creatinine) or elevated (E; >= 64 nmol/mmol creatinine). RESULTS. After 3 months of zoledronic acid, most N-group patients maintained normal levels; however, most E-group patients normalized their NTX levels (BC, 81%; HRPC, 70%; NSCLC/OST, 81%). In contrast, NTX levels normalized with pamidronate in 65% of BC, with placebo in 8% of HRPC, and in 17% of NSCLC/OST E-group patients. Normalized NTX correlated with improved overall survival versus persistently elevated NTX (significant for zoledronic acid-treated patients; trend for placebo-treated patients). Moreover, percentage reductions from baseline NTX levels correlated with benefits regardless of whether patients transitioned from E to N. CONCLUSIONS. Zoledronic acid normalizes or maintains normal NTX levels in most patients with bone metastases. Normalized NTX within 3 months of treatment, versus persistently elevated NTX, was associated with reduced risks of skeletal complications and death.