Comparing non-vertebral fracture risk reduction with osteoporosis therapies: looking beneath the surface

Data from pivotal trials of pharmacologic agents used to treat osteoporosis differ, suggesting that these agents vary in ability to reduce the risk of non-vertebral fractures (NVFs). However, variability among clinical trials in inclusion criteria, baseline characteristics, and definition of NVFs may account for many of these apparent differences. Data from pivotal trials of individual pharmacologic agents for osteoporosis differ, and suggest that differences may exist between anti-resorptive agents in their ability to reduce the risk of NVFs. Careful examination of these trials' inclusion criteria and patient characteristics indicates substantial differences between patient populations with respect to the baseline risk of NVFs. When baseline fracture risk is lower, the ability to produce a statistically significant reduction in fracture risk over the course of a clinical trial is reduced. Analysis of clinical trials reveals that the number and type of baseline vertebral fractures and also baseline bone mineral density, all associated with the risk of vertebral fracture, vary. The propensity to fall and patient frailty are additional factors associated with fracture risk that may influence study outcomes. One of the most significant variables, which also often differs considerably between trials, is the definition of an NVF. Variability between clinical trials in inclusion criteria, patients' baseline characteristics, and how NVFs are defined may account for much of the apparent difference between agents in their ability to reduce NVF risk.