Zoledronic Acid

Zoledronic acid (Zometa®), a parenteral bisphosphonate, is an inhibitor of osteoclast-mediated bone resorption and is used in the management of patients with cancer. Zoledronic acid 4mg is administered as an intravenous infusion over 15 minutes. In the treatment of bone metastases, zoledronic acid is the first and only bisphosphonate to demonstrate efficacy in patients with a broad range of tumour types and in multiple myeloma.

In well-designed trials, a single 4mg dose of zoledronic acid showed good efficacy in the treatment of patients with hypercalcaemia of malignancy. Zoledronic acid 4mg was superior to pamidronic acid 90mg, administered as a 2-hour infusion, as assessed by normalised serum calcium concentrations 10 days after administration. In conjunction with antineoplastic therapy, zoledronic acid was an effective long-term (up to 25 months) treatment for skeletal-related events in patients with bone metastases associated with multiple myeloma or solid tumours.

In patients with bone metastases secondary to breast cancer or bone lesions from myeloma, zoledronic acid was at least as effective as pamidronic acid, based on assessments of skeletal-related events 25 months after the start of treatment. In addition, compared with pamidronic acid, the overall risk of developing skeletal complications, including hypercalcaemia of malignancy, was significantly reduced in recipients of zoledronic acid. Compared with pamidronic acid,zoledronic acid reduced the risk of patients with breast cancer developing a skeletal-related event by an additional 20%. Zoledronic acid was significantly more effective than placebo on most efficacy measures in patients with bone metastases secondary to other solid tumours (e.g. lung, prostate) and showed sustained efficacy for up to 15 months. Preliminary data indicate that its efficacy in these patients is sustained for up to 24 months.

Estimates of the cost effectiveness of zoledronic acid in the treatment of prostate cancer were consistent with those of other bisphosphonates, and cost-effectiveness ratios were within limits considered acceptable economic value.

Zoledronic acid was generally well tolerated, with a tolerability profile similar to that of pamidronic acid and placebo. As with other bisphosphonates, deterioration of renal function has occasionally been reported in patients receiving zoledronic acid and monitoring of serum creatinine is recommended during treatment.

The efficacy of zoledronic acid is therefore well established in patients with hypercalcaemia of malignancy and, for up to 25 months, in the treatment of complications arising from metastatic bone disease in patients with multiple myeloma or solid tumours. The clinical profile of zoledronic acid compares favourably with that of pamidronic acid in patients with cancer and zoledronic acid has a more convenient administration schedule with the potential for better compliance. Thus, zoledronic acid is an effective bisphosphonate and is positioned to play an important role in the management of advanced cancer patients with bone metastases.