The effect of abaloparatide on the proximal femur in men with osteoporosis assessed by three-dimensional dual-energy X-ray absorptiometry

Abstract

Abaloparatide treatment significantly increased BMD at the LS, TH, and FN compared with placebo in men with osteoporosis in the phase 3 ATOM trial. The current study used 3D-DXA modeling to evaluate the effects of abaloparatide on cortical and trabecular compartments of the proximal femur in ATOM study participants. Proximal femur DXA images were retrospectively analyzed using 3D-DXA (3D-Shaper software v2.12.0, 3D-Shaper Medical, Barcelona, Spain) to evaluate changes in bone parameters from baseline at months 6 and 12 in all randomized men from the ATOM trial. Between-group comparisons were made for percent change from baseline data based on a mixed-effect repeated-measure model with treatment, visit, treatment-by-visit interaction, and type of DXA scanner as fixed effects. Other covariates include BMI, age, and baseline values of bone parameters. Abaloparatide treatment significantly increased integral volumetric BMD (vBMD) (3.7%), trabecular vBMD (7.0%), cortical thickness (1.1%), and cortical surface BMD (1.7%) at 12 mo compared to baseline (p < .0001). Changes were greater for abaloparatide compared to placebo for all 4 parameters (p < .01). Significant increases from baseline compared to placebo in integral vBMD (2.7% vs -0.1%, p < .0001) and trabecular vBMD (6.1% vs -0.6%, p < .0001) were also observed at 6 mo. In conclusion, in men with osteoporosis, abaloparatide improved proximal femur 3D-DXA parameters broadly consistent with results in postmenopausal women in the ACTIVE study, adding to the growing data on abaloparatide bone structure effects at the hip.

Keywords: 3D modeling; DXA; abaloparatide; cortical volumetric BMD; osteoporosis.

Graphical Abstract

Figure 1

Mean percent change in DXA and 3D-DXA parameters at the proximal femur from baseline to 12 mo. Abbreviations: 3D-DXA, three-dimensional DXA; ABL, abaloparatide; aBMD, areal BMD; Ct.sBMD, cortical sBMD; Ct.Th, cortical thickness; Ct.vBMD, cortical vBMD; Int.vBMD, integral vBMD; PBO, placebo; sBMD, surface BMD; Tb.vBMD, trabecular vBMD; vBMD, volumetric BMD. Longitudinal changes in hip DXA (aBMD) and 3D-DXA endpoints at 0, 6, and 12 mo after randomization. Data shown as mean ± 95% CI for percent change from baseline. ^**p < .01 vs PBO. ^***p < .0001 vs PBO. ^††p < .0001 vs baseline.

Figure 2

3D visualizations of the percent change from baseline in cortical vBMD, thickness, and sBMD. Abbreviations: ABL, abaloparatide; Ct.sBMD, cortical sBMD; Ct.Th, cortical thickness; Ct.vBMD, cortical vBMD; NS, not significant; PBO, placebo; sBMD, surface BMD; vBMD, volumetric BMD. Average spatial changes in 3D-DXA cortical endpoints at months 6 and 12. For each endpoint and treatment, anterior (left) and posterior (right) views of a standardized proximal femur model are shown. Blue-green colors represent increases and yellow-red colors represent decreases. NS: not significant against baseline.

Figure 3

2D cross-sectional changes in cortical and trabecular vBMD at month 12. Abbreviations: ABL, abaloparatide; PBO, placebo; vBMD, volumetric BMD. Cross sections displaying changes in cortical and trabecular vBMD at 12 mo in the ABL and PBO groups. Increases are presented in blue-green colors and decreases are presented in yellow-red colors.