Bone microarchitecture after discontinuation of denosumab in postmenopausal women with low bone mass — ASN Events
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Bone microarchitecture after discontinuation of denosumab in postmenopausal women with low bone mass (#50)

Ego Seeman 1 , Roger Zebaze 1 , Jose R Zanchetta 2 , David A Hanley 3 , Cesar Libanati 4 , Rachel B Wagman 4
  1. Austin Health, Repatriation Campus, Heidelberg, VIC, Australia
  2. Instituto de Investigaciones Metabólicas, Buenos Aires, Argentina
  3. Health Sciences Centre, University of Calgary, Calgary, AB, Canada
  4. Amgen Inc., Thousand Oaks, CA, USA

Aim: To quantify any microarchitecture changes following cessation of denosumab (DMAb).

Methods: Women completing a 12-month placebo controlled study of the effects of DMAb on microarchitecture (NCT00293813) who remained untreated for ≥ 12 months since last study visit were eligible for this study (NCT00890981). They had a single follow-up measurement of distal radius and distal tibia microstructure using HR-pQCT and forearm BMD using DXA. The primary endpoint was the percent change in distal radius cortical thickness relative to the baseline of the parent study. Secondary endpoints were trabecular morphology, BMD, and CTx and P1NP levels. Analysis of covariance included age, baseline values, effects of treatment in the parent study, time since last dose of DMAb or placebo.

Results: Forty and 39 subjects received DMAb or placebo 6 monthly, respectively. Mean (SD) age was 63.7 (6.1) years; mean (SD) time since last DMAb or placebo dose was 32.1 (2.6) months. After stopping DMAb, the increases in cortical thickness at the radius were lost but cortical thickness remained above the previous placebo group (p=0.077, table). The gain in cortical vBMD achieved with DMAb in the parent study was also attenuated; however, cortical vBMD remained higher than the former placebo group (p=0.023, table). Trabecular vBMD increased similarly in both groups. Results at the tibia were similar. Radial BMD (by DXA) also decreased but remained higher in former DMAb than former placebo groups: 2.1% at the 1/3 distal radius (p=0.018), 2.1% at the total radius (p=0.004), and 1.6% at the ultradistal radius (p=0.091).

Conclusion: Discontinuation of DMAb reverses the benefits achieved in microstructure and BMD. The increase in trabecular vBMD is probably an artifact produced by intracortical remodeling trabecularising the cortex.  If benefits of DMAb are to be retained treatment needs to be continued or followed by an alternative anti-resorptive.