G.O. Stewart

Prevention of appendicular bone loss in Paget’s disease following treatment with intravenous pamidronate disodium

It has been shown previously that intravenous pamidronate treatment for severe Pagets disease is associated with appendicular bone loss. This 2 year study was designed to determine whether cotreatment with calcitriol and a calcium supplement would prevent this. Intravenous pamidronate was used to treat 49 patients with symptomatic Pagets disease. Patients were stratified into two groups of differing biochemical severity based on hydroxyproline excretion (HypE) expressed as micromoles per liter of glomerular filtrate (GF): (1) a severe group with HypE > 10 micromol/L GF; and (2) a moderate group with HypE 5-10 micromol/L GF. Within each group, patients were randomly allocated to receive supplements of calcium and calcitriol (supplemented) or no supplements (unsupplemented) after initiation of pamidronate therapy. The severe group received 360 mg of pamidronate as six doses of 60 mg once weekly and the moderate group received 240 mg as four weekly doses of 60 mg. Patients were followed for 24 months following treatment and had serial bone densitometry of the forearm measured as well as urine and plasma biochemistry. When the groups were combined, the unsupplemented patients showed a decrease in bone mineral density (BMD) at the ultradistal forearm site, which persisted to 24 months. Those supplemented with calcium and calcitriol showed an increase in BMD and the difference between the two groups was significant at all times posttreatment (p < 0.03). When the groups were analyzed separately, those with moderate disease again showed significant differences in BMD between supplemented and unsupplemented patients at all timepoints. In the severe group, the differences did not reach statistical significance due to smaller patient numbers. Similar changes in BMD were also observed at the forearm shaft site. When serial parathyroid hormone (PTH) levels (with the moderate and severe groups combined) were plotted against time since treatment the rise in PTH in the supplemented patients was less than the rise in the unsupplemented patients (p < 0.04). These results suggest that forearm bone loss after intravenous pamidronate treatment for moderate-to-severe Pagets disease can largely be prevented by administration of calcium and calcitriol. The mechanism may be a blunting of the secondary hyperparathyroidism that occurs after intravenous pamidronate. These findings may have wider application in moderate-to-severe Pagets disease treated with other bisphosphonates.

Treatment of osteoporosis and Paget's disease.

Osteoporosis is a major public health problem. In women, the estimated lifetime risks of hip and vertebral fractures are 15% and 25%, respectively. The development of accurate and reproducible methods of assessing bone mineral density has enabled identification of persons at risk of fracture and assessment of response to treatment. Estrogen replacement therapy is effective in the prophylaxis of postmenopausal osteoporosis, and is the only therapy with well-proven antifracture efficacy. Fluoride can dramatically increase bone density, although a recent large, controlled study has demonstrated no effect on vertebral fractures. Bisphosphonates are emerging as a likely effective therapy for both idiopathic and glucocorticoid-induced osteoporosis. Calcium, vitamin D, calcitonin, and anabolic steroids may still have a role. Parathyroid hormone is a promising development that will need further study. Pagets disease is also common, affecting more than 3% of people over 40 years old. Calcitonin is an established therapy, although the bisphosphonates are a promising alternative.