Gallium nitrate for the treatment of bone metastases.

Gallium nitrate was originally developed as an antineoplastic agent; however, further studies have revealed that this drug has extremely potent effects on turnover of bone, and that low doses can be used to reduce bone resorption. Like the bisphosphonates, gallium nitrate has been studied in both malignant and in nonmalignant conditions. The results of randomized double blind studies have suggested that this drug has superior clinical efficacy relative to etidronate, calcitonin, and pamidronate for the acute control of cancer-related hypercalcemia. In patients with Paget's disease, low doses of gallium nitrate reduce biochemical parameters of accelerated bone turnover, including urinary excretion of calcium, hydroxyproline, and urinary collagen cross-linked N-telopeptides. Preliminary studies showed similar effects in patients with bone involvement from a wide variety of tumor types. Based on this high degree of clinical potency revealed in clinical studies, two randomized Phase III studies have been initiated in patients with bone metastases from breast carcinoma and bone involvement due to multiple myeloma. Both studies employ cyclic therapy with low dose gallium nitrate (i.e., 40 mg administered as a subcutaneous injection once daily for 2 weeks, followed by 2 weeks off treatment, recycled monthly). The endpoints of both studies are to document reductions in time to "morbid skeletal events," such as palliative skeletal radiotherapy, stabilizing orthopedic surgery, or pathologic fractures, as well as decreases in pain and analgesic requirements and improvements in mobility and other aspects of quality of life. These trials should provide definitive evidence of whether this agent is safe and effective as a treatment for bone metastases.