Receiving zoledronic acid for two year once every 12 weeks was noninferior to once every 4 weeks in this randomized study comparing the dosing schedules in patients with bone metastases.

These results from the CALGB 70604 study by the Alliance were presented by Andrew Louis Himelstein, MD, FACP, of the Helen F. Graham Cancer Center and Research Institute in Newark, Delaware, at the 2015 American Society for Clinical Oncology (ASCO) Annual Meeting in Chicago, Illinois.

Patients who have metastatic breast and prostate cancers and multiple myeloma are at risk of skeletal-related events (SRE), according to background information presented by Himelstein. SREs can include fractures, spinal cord compression, and surgery or radiation to the bone.

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Zoledronic acid is a bisphosphonate that is FDA approved to treat bone metastases. It reduces SREs when given every 3 to 4 weeks, but an optimal dosing interval has not been determined.

Current interest in bisphosphonates for reducing and delaying SREs focuses on maximizing the benefit and minimizing the risk of these agents.

Previous studies that looked at dosing of zoledronic acid included ZOOM and OPTIMIZE-2, both in breast cancer.1,2 The ZOOM study concluded that decreasing the administration of zoledronic acid might be possible, but that the effects on N-telopeptide needed to be investigated. N-telopeptide is elevated when bone turnover increases.

This study was unique in that it included patients with prostate cancer and multiple myeloma, as well as breast cancer, whereas the previous studies included only patients with breast cancer. Randomization started with the initial dose of zoledronic acid in this study, rather than at later doses.

The study enrolled 1,822 patients, with 911 patients receiving zoledronic acid every 4 weeks, and 911 patients receiving the drug every 12 weeks.

Patients’ dosages were based on their creatinine clearance. Both arms received the treatment for 2 years; SRE data was based on analyses of 408 patients treated every 4 weeks and 387 patients treated every 12 weeks.