Effects of Alendronate on Bone Metabolism in Glucocorticoid-Induced Osteoporosis Measured by18F-Fluoride PET: A Prospective Study

Abstract

Osteoporosis represents a significant side effect of glucocorticoid therapy, and alendronate has been reported to prevent this glucocorticoid-induced osteoporosis. Functional imaging with (18)F-fluoride PET allows quantitative analysis of bone metabolism in specific skeletal regions. However, only a few studies have quantitatively determined bone turnover and metabolism in glucocorticoid-induced osteoporosis by radiologic imaging techniques including PET. The aim of this study was to examine changes in regional bone remodeling and turnover as measured by (18)F-fluoride PET, the relationship between these measured changes and conventional bone metabolism parameters, and the effect of alendronate treatment. The study group consisted of 24 postmenopausal women (mean age, 59.7 y) who had various diseases, excluding rheumatoid arthritis, and had been treated with 10 mg or more of oral glucocorticoids (prednisolone equivalent) per day for more than 6 mo. Treatment with 5 mg of alendronate per day began at the time of study entry and continued for 12 mo. (18)F-fluoride PET was performed at baseline, 3 mo, and 12 mo to determine localized bone turnover, and the results were compared with other bone metabolism parameters. Lumbar spine standardized uptake values (SUVs) were significantly lower (P < 0.05) in the osteoporotic group (T-score < or = -2.5) than in the group that was healthy or osteopenic (T-score > -2.5). Patients treated with alendronate for 12 mo exhibited significant decreases in serum bone-specific alkaline phosphate (P < 0.05), urinary N-telopeptide for type I collagen (P < 0.01), lumbar spine SUV (P < 0.01), and femoral neck SUV (P < 0.01) in association with a gradual increase in bone mineral density (BMD) of the lumbar spine relative to the baseline value (P < 0.05). Although there was a significant correlation between BMD and SUV in the lumbar spine at baseline (P < 0.05), there was no correlation between the 2 variables at 12 mo of treatment with alendronate. Alendronate treatment resulted in significant decreases in bone metabolism and turnover in the lumbar spine. It also led to an increase in BMD of the lumbar spine in patients with glucocorticoid-induced osteoporosis. Our findings suggest that antiresorptive therapy has a direct bone-metabolism effect on skeletal kinetics in glucocorticoid-induced osteoporosis at the clinically important site of the lumbar spine.