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Test hip bone density on stopping alendronate

BMD at discontinuation – but not a year later – predicts 5-year fracture risk

Louise Prime

Wednesday, 07 May 2014

Hip bone mineral density (BMD) measured when postmenopausal women discontinue alendronate, as well as their age, helps to predict their risk of suffering a fracture during the following five years, research has shown. The FLEX study*, published in JAMA Internal Medicine, also showed that neither BMD measurements taken a year after drug discontinuation, nor levels of bone turnover markers, were associated with fracture risk.

Researchers in the Fracture Intervention Trial Long-term Extension (FLEX) randomly assigned women who were 61-86 years old and had already taken the bisphosphonate alendronate sodium for 4-5 years, to five further years of either alendronate or placebo. At baseline, they measured the women’s hip and spine BMD using dual X-ray absorptiometry (DXA), and their bone turnover markers (BTM); they re-measured women’s BTM at one and again at three years after randomisation.

For the current study, the researchers considered only the placebo group of 437 women. During five years’ placebo treatment, 94 (22%) of the women had at least one symptomatic fracture. Both older age and lower hip BMD at drug discontinuation were associated with an increased risk of having a clinical fracture during follow-up. But neither BMD measurements one year after discontinuing alendronate, nor BTM levels one to two years after stopping the drug, predicted fracture risk.

The study authors said: “Women with greater total hip bone loss two or three years after discontinuation may be at increased risk of fracture, but these results need to be confirmed in other studies before routine measurement of BMD after discontinuation of alendronate therapy can be recommended … In the meantime, short-term monitoring with BMD, BAP or NTX [two bone turnover markers] after discontinuation of four to five years of alendronate therapy does not appear to improve fracture prediction.”

The authors of an invited commentary** on this study wrote: “[It] is convincing because of its reliance on a clinical (symptomatic) fracture outcome rather than surrogate measures such as rates of BMD loss or changes in bone turnover marker levels. The study also raises new questions about appropriate clinical use and testing of bisphosphonates.”

They agreed that it appeared to support BMD at drug discontinuation, rather than taking frequent measurements later, as the best strategy to identify women at highest risk of fracture. They concluded: “In an era when we know much more about how to start alendronate therapy than how to stop it, the results of Bauer and colleagues suggest that identification of patients at high risk of fracture after treatment discontinuation is best accomplished by BMD measurement at the time of discontinuation rather than frequent short-term monitoring with BMD or bone turnover marker measurements after treatment discontinuation.”

* Bauer D C, Schwartz A, Palermo L, et al. Fracture Prediction After Discontinuation of 4 to 5 Years of Alendronate Therapy: The FLEX Study. JAMA Intern Med. Published online May 05, 2014. doi:10.1001/jamainternmed.2014.1232

** Gourlay M L and Ensrud K E. Bone Density and Bone Turnover Marker Monitoring After Discontinuation of Alendronate Therapy: An Evidence-Based Decision to Do Less. JAMA Intern Med. Published online May 05, 2014. doi:10.1001/jamainternmed.2014.162

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