Regular Bone Density Monitoring Doesn't Predict Fracture Risk After Bisphosphonate Discontinuation

The results of a secondary analysis of the FLEX trial do not support regular bone density monitoring within the first few years of discontinuing alendronate therapy.

Bone density check-ups may not be necessary for postmenopausal women within the first year after discontinuing bisphosphonate therapy, the results of a new study suggest. The secondary analysis of the Fracture Intervention Trial Long-term Extension (FLEX) study found that although a woman’s age and measures of bone density at the time she stopped taking medications for osteoporosis were able to predict her risk of breaking a bone, bone density testing 1 year later was not associated with fracture risk.

The FLEX trial evaluated the effects of discontinuing bisphosphonate therapy and randomized postmenopausal women aged 61 to 86 years who had taken alendronate for 4 to 5 years to receive alendronate or placebo for an additional 5 years, from 1998 to 2003. The results of the trial indicated that women in the placebo group were not at an increased risk for fractures when compared to those who had continued therapy. The current study, published online on May 5, 2014, in JAMA Internal Medicine, assessed trial results from the placebo group to determine whether hip and spine dual-energy x-ray absorptiometry (DXA) and bone turnover marker (BTM) measurements taken at the time of discontinuation and after 1 to 3 years of follow-up could predict fracture risk for the 5-year discontinuation period.

During the 5-year discontinuation period, 22% of women who discontinued therapy experienced at least 1 symptomatic fracture. The results indicated that older women and those with the lowest bone density at baseline were more likely to experience a fracture. After adjusting for age, women in the lowest third in terms of total hip bone mineral density (BMD) when they began taking placebo were 87% more likely to break a bone than were those with higher bone density levels. However, after 1 year of follow-up, changes in hip DXA and BTM were not associated with the risk of fracture. After 3 years, changes in BTM were still unrelated to fracture risk.

An accompanying commentary notes that the results do not support regular bone density monitoring within the first few years of discontinuing alendronate therapy.

“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,” the commentary authors write.

They suggest that longer studies are needed to help determine the best practices for managing patients who remain at a high fracture risk after discontinuation of bisphosphonate therapy.