Effect of denosumab treatment on the risk of fractures in subgroupsof women with postmenopausal osteoporosis

Denosumab reduces the risk of new vertebral and nonvertebral fractures. Previous trials suggest that the efficacy of antiresorptives on fractures might differ by patients' characteristics, such as age, bone mineral density (BMD), and fracture history. In the FREEDOM study, 7808 women aged 60 to 90 years with osteoporosis were randomly assigned to receive subcutaneous injections of denosumab (60 mg) or placebo every 6 months for 3 years. New vertebral and nonvertebral fractures were radiologically confirmed. Subgroup analyses described in this article were prospectively planned before study unblinding to evaluate the effect of denosumab on new vertebral and nonvertebral fractures across various subgroups. Compared with placebo, denosumab decreased the risk of new vertebral fractures in the overall study population over 3 years. This effect did not significantly differ for any of the nine subgroups analyzed (p  >  0.09 for all potential interactions). Denosumab also reduced all nonvertebral fractures by 20% in the full study cohort over 3 years. This risk reduction was statistically significant in women with a baseline femoral neck BMD T-score ≤ −2.5 but not in those with a T-score  >  −2.5; in those with a body mass index (BMI)  <  25 kg/m2 but not ≥ 25 kg/m2; and in those without but not with a prevalent vertebral fracture. These differential treatment effects were not explained by differences in BMD responses to denosumab. Denosumab 60 mg administered every 6 months for 3 years in women with osteoporosis reduced the risk of new vertebral fractures to a similar degree in all subgroups. The effect of denosumab on nonvertebral fracture risk differed by femoral neck BMD, BMI, and prevalent vertebral fracture at baseline.