Fracture Incidence and Characterization in Patients on Osteoporosis Treatment: The ICARO Study

Abstract

None of the available osteoporosis therapies have been shown to completely abolish the risk of fractures. In clinical practice, the outcome may be even poorer. In 880 patients prescribed with antiresorptives (alendronate, risedronate, and raloxifene) for >1 year, a fragility fracture was recorded in 8.9%/year of them. This incidence is considerably higher than that observed in randomized clinical trials, and it was significantly related to poor compliance and lack of supplementation with calcium and vitamin D. Osteoporotic fracture is one of the most important public health concerns among the elderly. Currently available therapies have been shown to significantly decrease the risk of fracture, although none of them completely abolishes this risk. In clinical practice, poor treatment response may also result from a number of other factors. The Incidence and ChAracterization of inadequate clinical Responders in Osteoporosis (ICARO) is a multicenter, observational study carried out in Italy. It aimed to analyze, in postmenopausal women with established osteoporosis, the risk factors for an "inadequate clinical response" to drug therapy, defined as the occurrence of new vertebral or nonvertebral fragility fractures in patients prescribed, for at least 1 year, alendronate, risedronate, or raloxifene, with a compliance >50%. In 880 patients treated with antiresorptive agents for a median of 2.0 years (95% CI: 1.0-4.5) years, the "inadequate clinical responder (ICR)" subjects over the observation period were 220 (25%), with an annual incidence of 8.9%. ICRs, compared with "adequate clinical responders (ACRs)," had more pretreatment fractures and were treated longer (2.8 versus 1.8 years; p < 0.001). After multiple adjustment for these confounding factors, significant determinants of inadequate clinical response were a poorer treatment compliance and a less frequent co-administration of calcium and vitamin D supplements. The incidence of fractures during treatment with antiresorptive agents in a clinical setting is considerably higher than that observed in randomized clinical trials. Inadequate compliance to treatment and lack of supplementation of calcium and vitamin D are major determinants of this poor response.