Zoledronic acid in the treatment of bone metastases from differentiated thyroid carcinoma

Background: Currently bisphosphonates are often administered to patients with osteolytic bone metastases from several neoplasms. Based on favorable experience in other cancers with bone metastases and the lack of effective treatment, we started to use zoledronic acid (ZA), a recently developed synthetic bisphosphonate drug, in the treatment of this disease. In the present study, we retrospectively evaluated the efficacy of ZA for bone metastases from differentiated thyroid carcinoma. Methods: The study consisted of 50 patients with bone metastases from differentiated thyroid carcinoma treated at the Cancer Institute Hospital of Tokyo between 1976 and 2008. Among them, 28 patients who did not undergo bisphosphonate therapy were defined as group A and 22 patients who received ZA therapy were defined as group B. The primary efficacy endpoint for ZA treatment was the reduction in the percentage of patients who developed skeletal-related events (SREs), including bone fracture, spinal cord compression, and hypercalcemia. A secondary endpoint was the interval between a presentation of bone metastases and appearance of SREs. Results: SREs occurred in significantly lower frequency in group B (3 of 22 patients, 14%) than group A (14 of 28 patients, 50%) (p = 0.007). The use of ZA significantly retarded the onset of the first SRE (p = 0.04). Two group-B patients developed bisphosphonate-related osteonecrosis of the jaw. Conclusion: Treatment with ZA was effective in reducing SREs or delaying their appearance in patients with bone metastases from differentiated thyroid carcinoma.