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.