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

Treatment with zoledronic acid (ZOL, 4mg) has proven effective for reducing the risk of skeletal-related events (SREs) in patients (pts) with multiple myeloma (MM), with a SRE incidence rate as low as 27% after 3.7 years' median follow-up (Morgan G, et al. Lancet Oncology 2011;12:743-52). Pts with normal bone metabolism may not require as intense a treatment schedule as pts with accelerated bone turnover. The Z-MARK study evaluated if pts with 1–2 years of prior intravenous (IV) bisphosphonate (BP) therapy can be treated safely long-term with less-frequent ZOL dosing based on bone turnover markers.

MM pts (N=121) who started IVBP therapy (ZOL or pamidronate) 1–2 years before enrollment and received ≥4 prior doses, with baseline calculated creatinine clearance (CrCl) of ≥30 mL/min, were enrolled. Pts received 4mg IV ZOL every (q) 4 or 12 weeks (wk) based on their most recent urinary N-telopeptide of type I collagen (uNTX) levels (q4 wk if uNTX ≥50 nmol/mmol Cr, q12 wk if uNTX <50 nmol/mmol Cr). Pts who developed a SRE or had disease progression requiring a change in MM therapy on study were treated q4 wk thereafter regardless of uNTX levels. The study's primary endpoint was the proportion of pts who experienced ≥1 SRE during study Year 1. Group A (ZOL q12 wk only, N=79) is compared with Group B (all others, N=42).

Of 121 pts enrolled, 52 discontinued early: 29 (36.7%) in A and 23 (54.8%) in B. Median time to discontinuation was ∼20 months (mo) in A and ∼24 mo in B. Median time on ZOL on study was 22.5 mo for A and 20.8 mo for B. The mean age was 63.8 years (range, 34–90) with approximately 1:1 male:female ratio. By International Staging System criteria, 81.0% in A and 69.1% in B were Stage I/II, while 15.2% and 19.0% were Stage III. Median time from initial MM diagnosis to enrollment was 18.4 mo in A and 18.6 mo in B. A majority of pts in both groups had ≥1 osteolytic lesions at enrollment (A, 65.8%; B, 76.2%). The median duration of prior IVBP therapy was 13.8 mo in A and 14.4 mo in B. At enrollment, 72.2% in A and 78.6% in B had ≥1 SRE. The baseline mean (standard deviation) for uNTX and calculated CrCl was 19.88 (8.8) nmol/mmol Cr, and 85.1 (31.8) mL/min in A and 24.1 (15.6) nmol/mmol Cr and 84.3 (40.0) mL/min in B. Four pts started ZOL at q4 wk vs 117 pts at q12 wk based on uNTX at study entry. Of 117 pts assigned to q12-wk dosing, 79 stayed on schedule throughout the study; 38 pts switched to q4 wk (14 for increased uNTX, 4 for SREs, and 20 for disease progression). Only 7 pts (5.8%; all in A) had a SRE in study Year 1 (3 pathologic fractures, 3 spinal cord compressions, 4 radiation to bone, 1 surgery to bone, 1 hypercalcemia of malignancy). In Year 2, only 5 pts (4.1%) had a SRE (1 pathologic fracture, 4 radiation to bone). Baseline uNTX (low: <28, high: ≥28) was predictive of SREs (hazard ratio=3.1, P=.06). Treatment was well-tolerated. The most common AEs were fatigue (26.4%), upper respiratory tract infection (24%), diarrhea (21.5%), pneumonia (21.5%), cough (20.7%), pyrexia (18.2%), arthralgia (17.4%), and nausea (17.4%); none were attributed to ZOL. Except for arthralgia, the incidence of these AEs was higher in B vs A. Serious AEs were reported in 29.1% in A and 59.5% in B. Overall, 19.8% of pts (15.2% A, 28.6% B) had an AE leading to ZOL discontinuation. At 48 wk, the median percentage change in uNTX was –13.3% in A and 0% in B. No change in the median serum Cr was observed in either group at 48 wk. Four deaths (2 from progression of MM, 1 from pneumonia, 1 unknown) were reported on study (not suspected to be related to ZOL). Four reports of osteonecrosis of the jaw (ONJ) were suspected to be related to ZOL (all in A, q12-wk dosing) at 22.2 mo median follow-up.

The final Z-MARK results show that bone marker-directed dosing is feasible and safe in pts with 1–2 years of prior IVBP therapy. The low incidence of SREs on study shows that less-frequent IVBP dosing beyond 1–2 years continues to reduce the SRE risk and may reflect changing treatment patterns for MM that include therapies with bone protective effects. Baseline uNTX (≥28 nmol/mmol Cr) trended toward significance for predicting SREs. Finally, this study, which prospectively evaluated ONJ beyond 3 years, demonstrated an incidence rate of 3.3%. Further studies and additional follow-up are needed to determine the potential predictive value and long-term benefits of bone marker-directed ZOL dosing in MM pts after standard IVBP treatment.

Raje:Amgen: Research Funding; Acetylon: Research Funding; Millenium: Consultancy; Celgene: Consultancy; Onyx: Consultancy; Eli-Lilly: Research Funding; Novartis: Consultancy. Off Label Use: Zoledronic acid (4 mg every 3–4 weeks) is indicated for the treatment of patients with multiple myeloma and patients with bone metastases from solid tumors. Vescio:Novartis Pharmaceuticals Corporation: Speakers Bureau. Hadala:Novartis Pharmaceuticals Corporation: Employment. Warsi:Novartis: Equity Ownership; Novartis: Employment. Ericson:Novartis Pharmaceuticals Corporation: Employment, Stocks Other. Anderson:Novartis Pharmaceuticals Corporation: Consultancy.