Effect of Low Dose Denosumab on Bone Mineral Density in Postmenopausal Women with Osteoporosis After a Transition From 60mg Dose: A Prospective Observational Study

Abstract

Introduction: Denosumab is an effective antiresorptive molecule and reduces the risk of fracture in postmenopausal osteoporosis. Cessation of denosumab therapy however is associated with rapid declines in bone mineral density (BMD), rises in bone remodelling and an increased risk of fracture. We evaluated the effect of low dose denosumab (30mg every 6 months) on the prevention of bone loss following a switch from standard dose (60mg of denosumab every 6 months) in a prospective observational study. Methods We recruited 114 women 50–90 years of age with postmenopausal osteoporosis at a moderate fracture risk without prior fragility fractures who had been on denosumab 60mg every 6 month. These women switched to low dose denosumab 30mg every 6 months. Mean % change in lumbar spine (LS), femoral neck (FN), total hip (TH) and 1/3 distal radius (1/3RAD) BMD at 12 and 24 months were evaluated. Predictors for change in BMD were explored. Subgroup analysis for patients on denosumab 60mg every 6 months for < 3 years and for ≥ 3 years before switching to low dose denosumab 30mg was explored. Results At 12 months, there was an increase in LS BMD mean % change (+ 2.03%, 95% CI 1.18–2.88, p < 0.001). BMD was stable at the hip and radial sites. Age was found to be a predictor of the mean % change of LS BMD for the overall sample. At 24 months, there was a further increase in LS BMD mean % change (+ 3.44%, 95% CI 1.74–5.12, p < 0.001), with stable BMD at other skeletal sites. The 12 month mean BMD % change at the LS (p = 0.015), FN (p < 0.001), TH (p < 0.001), and 1/3 RAD (p < 0.001) were found to be predictors of the 24 month mean BMD % change. No clinical fractures were reported during 24 months of follow up. Conclusion We observed stable BMD following a switch from denosumab 60mg every 6 months to 30mg every 6 monhts in this prospective observational study conducted in postmenopausal women at a moderate fracture risk