In a recent systematic review, Fink and colleagues attempted to summarize the published evidence of the efficacy and safety of long-term (> 3 years) therapy for osteoporosis.1 Unfortunately, they arrived at very limited and tentative conclusions because, as they point out, of the paucity of such evidence.
Why long-term studies stop short
Only 3 of the several tens of placebo-controlled fracture end-point studies (about 58 trials and observational studies) that Fink and colleagues reviewed evaluated treatment for more than 3 years. The nonavailability of longer-term studies is the direct consequence of a requirement by regulatory agencies for a 3-year fracture end-point study in order to register a new drug for osteoporosis. Hence, longer, placebo-controlled studies do not benefit the industry sponsor, and enrolling patients with osteoporosis or who are at high risk for fracture in any, much less long, placebo-controlled trials is now considered to be unethical.
What the authors did observe
From this limited set of information with which to evaluate, Fink and colleagues observed that long-term therapy with raloxifene reduces the risk of vertebral fractures but is associated with thromboembolic complications. In addition, treatment for more than 3 years with bisphosphonates reduces the risk of vertebral and nonvertebral fractures but may increase risk of rare adverse events (including femoral shaft fractures with atypical radiographic features).
The bisphosphonate holiday. The authors refer to the even more limited evidence about the effects of discontinuing bisphosphonate therapy. Unlike the rapid loss of bone mass density (BMD) and fracture protection upon stopping estrogen or denosumab, the offset of these treatment benefits is slower when bisphosphonates are discontinued. This, coupled with concern about increasing risk with long-term bisphosphonate therapy, led to the confusing concept of a “bisphosphonate holiday.” While recommendations to consider temporary discontinuation of bisphosphonates in patients at low risk for fracture have been made by expert panels,2 very little information exists about the benefits/risks of this strategy, how long the treatment interruption should be, or how to decide when and with what to restart therapy. Unfortunately, overall, Fink and colleagues’ observations provide little practical guidance for clinicians.
Continue to: What we can learn from longer term and recent studies of ideal treatment...