THU445 Complicated Course And Management After Denosumab Discontinuation: A Case Report

Disclosure: I. Arora: None. L. Ceglia: None. Background: Discontinuation of denosumab (DMAb) can lead to rapid bone loss and sometimes multiple vertebral fractures (VFx). Here we present such a case and related challenges in management. Case: A 56-year-old perimenopausal female presented for management of osteoporosis (OP) complicated by multiple VFx following a missed dose of DMAb in 8/2020. Past bone health history was notable for treatment with alendronate for approximately 11 years as a premenopausal woman. During a drug “holiday” in 2015, she was found to have a decline in bone mineral density (BMD). She was advised to start treatment with DMAb in 8/2016. She was adherent to DMAb injections for 4 years but missed a dose in 8/2020 due to the COVID-19 pandemic. In 1/2021, she developed back pain with no trauma and was diagnosed with VFx of T7, T10 and T12. She underwent vertebroplasty of all 3 vertebrae by 2/2021. DMAb was resumed in 2/2021 and 8/2021. Labs were only notable for hypercalciuria for which hydrochlorothiazide (HCTZ) was initiated. In 11/2021 she presented with new symptomatic VFx of T5, T9 and T11. In 12/2021 (3 weeks post 3 new VFx), serum fasting C-telopeptide (CTX) was 79 pg/mL. Teriparatide or abaloparatide were avoided due to hypercalciuria and potential BMD losses with this transition. Thus in 1/2022, she started romosozumab (ROMO) in an attempt to prevent new VFx. CTX was initially 78 pg/mL and rose rapidly over 3 months to 325 pg/mL with new back pain in 4/2022. No new VFx were detected; however, ROMO was discontinued due to the rise in CTX level. In 5/2022, she received a dose of zoledronic acid (ZOL). It suppressed CTX from 325 to 131 pg/mL by 6/2022. She received another 2 doses of ZOL in 8/2022 and 11/2022 due to rebound rises in CTX. Of note, as she reported ongoing menopausal complaints, transdermal low-dose estradiol therapy was started in 11/2022. She has not had a new VFx in more than 1 year. Hypercalciuria persisted throughout 2022 requiring rising doses of (HCTZ). DXA in 12/2022 was stable vs. 12/2021 without evidence of significant BMD loss. Discussion: This case not only highlights the known risk for multiple VFx in a patient discontinuing long-term DMAb treatment (4 years), but also the risks for such VFx complications in women of younger age during menopausal transition and a history of vertebroplasty. In addition, this report does not support transitioning from long-term DMAb to ROMO in order to prevent a rapid increase in the bone resorption marker, CTX. Rather, treatment with ZOL every 12 weeks based on frequent CTX monitoring successfully maintained BMD stable following long-term DMAb discontinuation. Presentation: Thursday, June 15, 2023