Bisphosphonate treatment of lytic bone metastases

Tumour-induced osteolysis or lytic bone disease is mediated by osteoclast activation. Osteoclasts can be activated directly by tumour products or indirectly through an influence on other cells. By reducing osteoclastic activity, bisphosphonates inhibit bone resorption. Pamidronate is a second-generation amino-bisphosphonate that is a potent inhibitor of osteoclastic activity. In multiple myeloma, a phase III study has shown that the proportion of patients at the end of 21 months who had any skeletal event was significantly lower in the pamidronate group (38%) than in the placebo group (58%). The therapeutic benefit was independent of the type of antimyeloma chemotherapy. Patients who received pamidronate had significant decrease in bone pain and delayed deterioration in performance status and quality of life. Overall there was no survival advantage in patients who received pamidronate. In similar fashion, in 2 phase III breast cancer trials, patients who received pamidronate had fewer skeletal events, decrease in bone pain and analgesic use, and slower deterioration of performance status that in those patients receiving placebo. Again, there was no survival advantage in these patients. Recent studies suggest that the bisphosphonates clodronate can prevent the development of bone metastases in patients with breast cancer.