Bone mineral density after transitioning from denosumab to alendronate

Context
There are few studies on patients transitioning from denosumab to bisphosphonates.

Objective
To investigate patient characteristics and changes in bone mineral density (BMD) after transitioning from denosumab to alendronate.

Design
Randomized, open-label, 2-year crossover Denosumab Adherence Preference Satisfaction (DAPS) study (NCT00518531).

Setting
25 study centers in the US and Canada.

Patients
Treatment-naïve postmenopausal women with BMD T-scores from −2.0 to −4.0.

Interventions
This post hoc analysis evaluated women randomized to subcutaneous denosumab 60 mg every 6 months in year 1 followed by once-weekly oral alendronate 70 mg in year 2.

Main Outcome Measure
A 3% BMD threshold identified participants who lost, maintained, or gained BMD in year 2 on alendronate.

Results
Of 126 participants randomized to denosumab, 115 (91%) transitioned to alendronate in year 2. BMD increased by 3% to 6% with denosumab in year 1 and by 0% to 1% with alendronate in year 2. After transitioning to alendronate, most participants maintained or increased BMD; 15.9%, 7.6%, and 21.7% lost BMD at the lumbar spine, total hip, and femoral neck, respectively. Few participants fell below their pretreatment baseline BMD value; this occurred most often in those who lost BMD in year 2. Women who lost BMD with alendronate in year 2 also showed a greater percent change in BMD with denosumab in year 1. The BMD change in year 2 was similar regardless of baseline characteristics or adherence to oral alendronate.

Conclusion
Alendronate can effectively maintain the BMD gains accrued after 1 year of denosumab in most patients, regardless of baseline characteristics.