Gallium nitrate inhibits accelerated bone turnover in patients with bone metastases

Bone metastases are a major source of morbidity in patients with cancer. Previously, we found that gallium nitrate was a highly effective treatment for cancer-related hypercalcemia. Laboratory studies have shown that this drug inhibits bone resorption in vitro and that short-term treatment in vivo increases the calcium content of bone. We evaluated the clinical effects of gallium nitrate on biochemical parameters of increased bone turnover in 22 patients with bone metastases. Treatment with gallium nitrate for five to seven days caused a median reduction in 24-hour urinary calcium excretion of 66% relative to baseline measurements (P less than .01). Hydroxyproline (OHP) excretion was also significantly reduced (P less than .01). The greatest reduction in hydroxyprolinuria occurred in patients with high baseline excretion. Ionized serum calcium and serum phosphorous declined significantly after treatment (P less than .01 for each). Serum immunoreactive parathyroid hormone (PTH) increased significantly (P less than .01), as did serum levels of 1,25 (OH)2-vitamin D3 (P less than .05). Urinary phosphorous excretion and serum levels of 25-OH-vitamin D3 were not significantly changed. No major toxic reactions occurred as a result of this treatment. These results indicate that gallium nitrate significantly reduces biochemical parameters associated with accelerated bone turnover and that this agent may be useful for preventing pathologic conditions associated with bone metastases.