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Bisphosphonates, calcitonin, raloxifene similarly effective in preventing nonvertebral fractures
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Results of a large observational study showed no difference in the effectiveness of bisphosphonates in preventing nonvertebral fractures.
There is likely no single superior drug for osteoporosis, according to researchers from Brigham and Women’s Hospital, Harvard Medical School and Boston University. The researchers conducted a cohort study of 43,135 older adults who were new recipients of oral bisphosphonates, nasal calcitonin and raloxifene (mean age, 79; 96% women). During one year of follow-up, there were 1,051 nonvertebral fractures (2.62 fractures per 100 person-years).
Differences in nonvertebral fracture risk between alendronate and risedronate (HR=1.01) or raloxifene (HR=1.18) were small. Individuals who nasal received calcitonin (HR=1.40) had more nonvertebral fractures compared with alendronate recipients.
Those with a history of fracture experienced the most nonvertebral fractures within one year with raloxifene (HR=1.78) compared with alendronate. These data contrast with previous findings that suggest risedronate is more effective than alendronate in preventing nonvertebral fractures, according to the researchers. – by Katie Kalvaitis
Observational cohort studies, particularly those based on the incomplete data available from Medicare pharmaceutical benefit plans, are effective tools in ascertaining the demographics of patients prescribed a particular therapy. However, extreme caution should be applied when such studies attempt to compare efficacy of different agents, as was done in this study, which purports to show comparable nonvertebral fracture efficacy. Such a finding is surprising, given that antiresorptive therapies primarily strengthen bones and reduce fracture risk by reducing the rate of bone turnover, which in turn results in increased bone mineral density, and the antiresorptive efficacy for these agents at approved doses is alendronate is better than risedronate which is between than raloxifene.
Patient care would benefit from randomized, controlled studies comparing the benefits and risks of different therapies. Unfortunately, identifying a funding source for each study is a major challenge. In the vacuum created by the lack of controlled comparative efficacy studies it is tempting to view observational studies such as the one by Cadarette et al. as ‘filling the gap.’ However, the risk of such studies, with their major imbalances and confounders, is that even when the authors list limitations so profound as to invalidate the main result, the take-home message will be that ‘there might not be a single clearly superior drug therapy for preventing fractures in older adults with osteoporosis.’ It is thus possible that the use of uncontrolled, observational cohort studies is to compare the relative efficacy of drugs might not improve patient care, but harm it.
– David B. Karpf, MD
Attending, Osteoporosis & Metabolic Bone Disease Clinic,
Stanford University Hospital & Clinics
For more information:
- Ann Intern Med. 2008;148:637-646.