Osteoporosis treatment and fracture incidence: the ICARO longitudinal study

Abstract

None of the available osteoporosis therapies completely abolish the risk of fracture. Among 862 patients on treatment with antiresorptive agents (alendronate, risedronate, and raloxifene) for >1 year a fragility fracture was observed in 9.5%/year. This incidence is considerably higher than that observed in randomized clinical trials. Available osteoporosis therapies reduced in randomized controlled trials (RCTs) the risk of fracture by 30-50%. The proportion of patients suffering from new fractures while on active treatment ("inadequate clinical treatment response" or ICR) can be derived from the data of the RCTs, where confounding factors are usually controlled by the exclusion criteria. In the retrospective part of the ICARO study we observed a 8.9% annual incidence of ICR. Here we report the results of the longitudinal part of the study. The study includes 862 women with severe postmenopausal osteoporosis. Ninety-two of these patients (10.7%) were defined as having ICR (9.5%/year) during therapy with antiresorptive drugs (alendronate, risedronate, and raloxifene) for at least 1 year. The ICR patients were comparable to patients who did not sustain clinical fractures with regard to body mass index, follow-up duration, number of prevalent vertebral fractures, type of osteoporosis treatment, proportion of patients taking calcium and vitamin D supplements, and compliance with treatment. Those with ICR were significantly older (p=0.032) and more frequently had multiple vertebral deformities (p=0.013). The incidence of ICR during treatment with antiresorptive agents among patients with severe postmenopausal osteoporosis in a routine setting is considerably higher than that observed in randomized clinical trials.