The duration of denosumab treatment and the efficacy of zoledronate to preserve bone mineral density after its discontinuation.

CONTEXT Zoledronate is used to prevent bone loss following denosumab discontinuation but its efficacy differs among studies. OBJECTIVE To test if the duration of denosumab treatment affects the efficacy of subsequent zoledronate infusion. DESIGN Multicenter, prospective cohort study. SETTING Two Greek and one Dutch bone centers. PATIENTS Postmenopausal women (n=47) who received a single zoledronate infusion 6 months after the last denosumab injection and were followed for 1 year. Twenty-seven women received ≤ 6 denosumab injections (≤ 6 Group) and twenty received > 6 denosumab injections (> 6 Group). MAIN OUTCOME MEASURE Changes in lumbar spine (LS) BMD. RESULTS At 12 months LS- BMD values were maintained in the ≤6 Group (0.98±0.10 to 0.99±0.9/ g/cm 2 p=0.409) but decreased significantly in the >6 Group (1.0 ± 0.11 to 0.93 ± 0.12 g/cm 2, p 6 Group (-7.0%). In the whole cohort the duration of denosumab treatment was negatively correlated with the percentage change of LS-BMD (rs:-0.669, p<0.001) but not with the change of FN-BMD. Bone turnover markers increased in all patients 6 months following zoledronate administration with no difference between the two groups. CONCLUSIONS The duration of denosumab treatment significantly affects the efficacy of subsequent zoledronate infusion to maintain BMD gains. Frequent follow-up of patients treated with denosumab longer than 3 years is advisable as additional therapeutic interventions may be needed.