https://orcid.org/0000-0001-8518-2103
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Donal Fitzpatrick, Rosaleen Lannon, Kevin McCarroll, Letter to the Editor From Fitzpatrick et al: “Zoledronate After Denosumab Discontinuation: Is Repeated Administrations More Effective Than A Single Infusion?”, The Journal of Clinical Endocrinology & Metabolism, Volume 109, Issue 12, December 2024, Pages e2358–e2359, https://doi.org/10.1210/clinem/dgae491
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Dear Editor,
We read with interest the study by Grassi et al (1), which is the first to examine the application of European Calcified Tissue Society (ECTS) recommended bone turnover marker (BTM) cutoffs in guiding zoledronic acid therapy post denosumab cessation (2). The findings are very important as 75% of patients who stopped denosumab required a second infusion of zoledronic acid 6 months after the first (using a CTX cutoff >0.280 ng/L). Furthermore, despite 2 infusions there was significant loss of bone mineral density (BMD) at the lumbar spine (mean 5.4%) with 9.6% developing new fractures.
This fracture incidence is concerning and more than anticipated. Notably, 2 patients with vertebral fractures had lumbar spine T scores of less than −3.0. All had prior vertebral fractures, but their recency was not documented. Additionally, one patient with an incident hip fracture with a T score of −4.1 at the neck of the femur was already at high risk of fracture. These 3 patients typically would not be advised to stop denosumab, and the decision to transition was driven by patient choice. It is concerning that one patient with a new vertebral fracture had a spine T score of −1.3, though their initial and follow-up CTX were respectively very high (1136 ng/mL) and high (413 ng/mL) with a large associated decline in spine BMD (10.0%). This supports the limited existing research (3, 4) highlighting the importance of BTMs during the “rebound period” in predicting BMD loss at the lumbar spine.
