Bone Marker-Directed Dosing of Zoledronic Acid for the Prevention of Skeletal Complications in Patients with Multiple Myeloma: Results of the Z-MARK Study.

PURPOSE Zoledronic acid (ZOL) given every 3 to 4 weeks can reduce skeletal-related events (SRE) in patients with bone lesions from multiple myeloma. This study evaluated efficacy and safety of less-frequent ZOL dosing based on bone turnover markers in patients with 1 to 2 years of prior bisphosphonate therapy. EXPERIMENTAL DESIGN Patients received ZOL (4 mg) every 4 or 12 weeks based on urinary N-telopeptide of type 1 collagen (uNTX) levels (every 4 weeks if uNTX ≥50 nmol/mmol creatinine, every 12 weeks if uNTX < 50). RESULTS Of 121 patients enrolled (mean age, 63.8 years; median follow-up, 21 months), 4 patients started ZOL every 4 weeks and 117 received ZOL every 12 weeks based on uNTX at study entry. All 4 patients who initiated ZOL every 4 weeks switched to every 12 weeks due to decreased uNTX. Thirty-eight of 117 patients who initiated ZOL every 12 weeks switched to ZOL every 4 weeks due to disease progression (n = 20), increased uNTX (n = 14), and SREs (n = 4). Overall SRE incidence was low; 7 (5.8%) and 5 (4.9%) patients experienced an SRE during years 1 and 2, respectively. Mean (SD) SRE rate at year 2 was 0.01 (0.03) per person-year. The 2-year incidence rate for osteonecrosis of jaw was 3.3%. Four deaths were reported, none related to ZOL. CONCLUSIONS Less frequent ZOL dosing (every 12 weeks over 2 years) maintains a low SRE rate and can be safely administered for up to 4 years.