Impact of Zoledronic Acid on Bone Mineral Density and Trabecular Score Following Denosumab Discontinuation in Older Adults in Long-Term Care.

Discontinuation of denosumab can result in rebound bone loss and increased vertebral fracture risk. In residents of long-term care communities (LTCCs) with osteoporosis, there is limited data on managing the risks after discontinuation. We investigated the impact of a single dose of zoledronic acid on bone density and microarchitecture following two years of denosumab treatment. In an open-label, one-year extension study following a two-year double-blind, placebo-controlled, randomized clinical trial, 39 older adults aged 65 years and above, who were residents of LTCCs and participants in the PROUD (PReventing Osteoporosis Using Denosumab) trial, received a single 5 mg dose of zoledronic acid after completing four doses of denosumab 60 mg during the PROUD trial. We aim to evaluate the effects of a single 5 mg dose of zoledronic acid on bone mineral density (BMD) at the lumbar spine, total hip, femoral neck, and one-third radius, as well as on the spine trabecular bone score (TBS), over a one-year period. Additionally, we surveyed patients for fractures. Our study included 27 women and 12 men, with a mean age of 81.5 years. Twelve months after the administration of zoledronic acid, the mean percent changes from the end of the denosumab trial showed no significant decline in any of the BMD sites in both women and men. In women, the mean percent changes were as follows: spine 0.97 (95% CI: -0.7 to 2.7, p = 0.242) and total hip -0.10 (95% CI: -2.3 to 2.1, p = 0.927). In men, the changes were -0.32 (95% CI: -3.7 to 3.1, p = 0.832) for the spine and 1.79 (95% CI: -0.7 to 4.3, p = 0.139) for the total hip. These findings indicate no evidence of rebound bone loss. In women, TBS significantly increased by 3.9% (95% CI: 0.8 to 5.8, p = 0.007), suggesting improved bone microarchitecture. In men, there was a trend toward improvement in TBS, with an increase of 3.3% (95% CI: -4.0 to 13.0, p = 0.054). There were no reported fragility fractures among participants during the post-denosumab period. In residents of LTCCs with osteoporosis receiving a single 5 mg dose of zoledronic acid following two years of denosumab, we found no evidence of a loss in BMD or TBS. Further, participants experienced enhanced bone microarchitecture.