Bone 56 (2013) 482–488
Contents lists available at ScienceDirect
Bone journal homepage: www.elsevier.com/locate/bone
Original Full Length Article
Improvements in hip trabecular, subcortical, and cortical density and mass in postmenopausal women with osteoporosis treated with denosumab☆ Harry K. Genant a,b,⁎, Cesar Libanati c, Klaus Engelke d,e, Jose R. Zanchetta f, Arne Høiseth g, Chui Kin Yuen h, Sigtas Stonkus i, Michael A. Bolognese j, Edward Franek k,l, Thomas Fuerst m, Hoi-Shen Radcliffe n, Michael R. McClung o a
UCSF, 505 Parnassus Ave, San Francisco, CA 94143, USA Synarc Inc., 575 Market Street, 17th Floor, San Francisco, CA 94105, USA c Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA 91320, USA d Institute of Medical Physics, University of Erlangen, Henkestr. 91, 91052 Erlangen, Germany e Synarc Inc., Lübecker Strasse 128, 22087 Hamburg, Germany f Instituto de Investigaciones Metabόlicas, Libertad 836, C1012AAR Buenos Aires, Argentina g Curato Røntgen, Stenersgt 1a, 0050 Oslo, Norway h SIGMA Canadian Menopause Society, 205-1089 W Broadway, Vancouver, BC V6H 1E5, Canada i Klaipeda University Hospital, Liepojos 41, 92228 Klaipeda, Lithuania j Bethesda Health Research, 10215 Fernwood Road, #40, Bethesda, MD 20879, USA k Central Clinical Hospital MSWiA, ul Woloska 137, 02-507 Warsaw, Poland l Medical Research Center, Polish Academy of Sciences, 5 Pawinskiego Str., 02-106 Warsaw, Poland m Synarc Inc., 7707 Gateway Blvd, Newark, CA 94560, USA n Amgen Ltd., 240 Cambridge Science Park, Cambridge, CB4 0WD, UK o Oregon Osteoporosis Center, 5050 NE Hoyt Street, Suite 626, Portland, OR 97213, USA b
a r t i c l e
i n f o
Article history: Received 9 February 2013 Revised 31 May 2013 Accepted 9 July 2013 Available online 17 July 2013 Edited by: R. Baron Keywords: Bone mineral density Bone mineral content Denosumab Hip Osteoporosis Quantitative computed tomography
a b s t r a c t In the FREEDOM study, denosumab treatment (60 mg every 6 months) decreased bone resorption, increased bone mineral density (BMD), and reduced new vertebral, nonvertebral, and hip fractures over 36 months in postmenopausal women with osteoporosis. In a subset of these women, hip quantitative computed tomography (QCT) was performed at baseline and months 12, 24, and 36. These scans were analyzed using Medical Image Analysis Framework (MIAF) software, which allowed assessment of total hip integral, trabecular, subcortical, and cortical compartments; the cortical compartment was further divided into 2 areas of interest (outer and inner cortex). This substudy reports changes in BMD and bone mineral content (BMC) from baseline and compared placebo with denosumab over 36 months of treatment (placebo N = 26; denosumab N = 36). Denosumab treatment resulted in significant improvements in total hip integral volumetric BMD (vBMD) and BMC from baseline at each time point. At month 36, the mean percentage increase from baseline in total hip integral vBMD and BMC was 6.4% and 4.8%, respectively (both p b 0.0001). These gains were accounted for by significant increases in vBMD and BMC in the trabecular, subcortical, and cortical compartments. In the placebo group, total hip integral vBMD and BMC decreased at month 36 from baseline by −1.5% and −2.6%, respectively (both p b 0.05). The differences between denosumab and placebo were also significant at months 12, 24, and 36 for integral, trabecular, subcortical, and cortical vBMD and BMC (all p b 0.05 to b 0.0001). While the largest percentage differences occurred in trabecular vBMD and BMC, the largest absolute differences occurred in cortical vBMD and BMC. In summary, denosumab significantly improved both vBMD and BMC from baseline and placebo, assessed by QCT MIAF, in the integral, trabecular, subcortical, and cortical hip compartments, all of which are relevant to bone strength. © 2013 The Authors. Published by Elsevier Inc. All rights reserved.
☆ This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-No Derivative Works License, which permits non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited. ⁎ Corresponding author at: UCSF/Synarc Inc., 7 Tara Hill Road, Tiburon, CA 94920, USA. Fax: +1 415 366 2220. E-mail addresses:
[email protected] (H.K. Genant),
[email protected] (C. Libanati),
[email protected] (K. Engelke),
[email protected] (J.R. Zanchetta),
[email protected] (A. Høiseth),
[email protected] (C.K. Yuen),
[email protected] (S. Stonkus),
[email protected] (M.A. Bolognese),
[email protected] (E. Franek),
[email protected] (T. Fuerst),
[email protected] (H.-S. Radcliffe),
[email protected] (M.R. McClung). 8756-3282/$ – see front matter © 2013 The Authors. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.bone.2013.07.011
H.K. Genant et al. / Bone 56 (2013) 482–488
Introduction Dual-energy x-ray absorptiometry (DXA) remains the most widely used technique to identify patients at risk for fracture and assess response to osteoporosis therapy in the clinical setting. However, DXA is a 2-dimensional measurement of areal bone mineral density (aBMD) and is therefore limited in the assessment of bone geometry, and is not able to fully distinguish the trabecular and cortical bone compartments. Recent imaging and technical developments allow improved in vivo evaluations of skeletal sites of clinical relevance in subjects at risk for fracture. In particular, QCT advancements now enable precise and detailed assessments within the trabecular and cortical bone compartments [1,2]. There is increasing evidence that both trabecular and cortical bone are important determinants of strength in patients with osteoporosis who experience fracture [3–6]. Assessing both trabecular and cortical bone is important as these compartments may lose or gain bone differently with aging and in response to therapies, impacting their specific relative contributions to bone strength [7–9]. The amounts of both trabecular and cortical bone decrease as osteoporosis progresses; however, as trabecular bone disappears with increasing bone loss, the extent to which the cortical compartment contributes to bone strength increases [8–10]. Use of new image acquisition and analysis techniques can provide information on the effects of treatments on bone density and geometrical changes in the trabecular and cortical compartments. Quantitative computed tomography (QCT) complements DXA by 3-dimensionally measuring volumetric BMD (vBMD) and bone mineral content (BMC), commonly referred to as bone mass; these can be measured not only within the total bone but also separately in the individual bone compartments [2,11]. Denosumab (Prolia®; Amgen Inc., Thousand Oaks, CA, USA) is a fully human monoclonal antibody that inhibits RANKL, a key modulator of osteoclast formation, function, and survival [12–15]. The mechanism of action of denosumab leads to rapid and maximal reductions in bone resorption throughout the trabecular and cortical compartments [16]. Clinical trials, including the FREEDOM (Fracture REduction Evaluation of Denosumab in Osteoporosis every 6 Months) study, have established that denosumab treatment results in a significant improvement in DXA aBMD at the hip in the majority of subjects [17–23], and these gains significantly explained the observed fracture risk reductions [24]. Areal BMD gains are influenced by both trabecular and cortical changes, which cannot be precisely distinguished with DXA. In view of the strong association between gains in aBMD and the fracture risk reductions observed with denosumab treatment, and that both trabecular and cortical bone determine whole-bone strength, we have hypothesized and previously demonstrated using standard QCT analysis software that total hip BMD changes associated with denosumab would be apparent in both the trabecular and cortical compartments [25]. To further document and characterize the magnitude and distribution of the changes in BMD and BMC at the hip, and understand the relative contribution of each compartment, including the subcortical compartment, we applied Medical Image Analysis Framework (MIAF) software to hip QCT scans obtained in a subset of women who participated in the FREEDOM study. MIAF improves the 3D segmentation of the hip, and thus provides a more comprehensive method to evaluate integral and compartment changes [26,27]. Methods Study design and data source FREEDOM was an international, multicenter, randomized, doubleblind, placebo-controlled study. Subjects were randomly assigned to receive subcutaneous injections of either placebo or denosumab
483
60 mg every 6 months for 36 months. All women received daily supplementation of calcium (≥ 1000 mg) and vitamin D (≥ 400 IU). The methods and results of the overall study have been previously reported [20]. Study centers in the FREEDOM study with expertise and access to a qualified QCT scanner invited subjects to participate in a QCT substudy of the lumbar spine and hip measurements. The methods and primary results of this QCT substudy have been reported [25]. In this substudy of the FREEDOM study, hip QCT scans were used to non-invasively further assess changes in hip vBMD and BMC associated with placebo and denosumab treatment over 36 months.
Participants The FREEDOM study included postmenopausal women aged 60 to 90 years with a DXA BMD T-score of b−2.5 at either the lumbar spine or total hip, and not b−4.0 at either site. Women were excluded if they had any severe or N2 moderate vertebral fractures, had conditions that affected bone metabolism, had taken oral bisphosphonates for N3 years, or received intravenous bisphosphonates, fluoride, or strontium treatment for osteoporosis within the last 5 years. The protocol was approved by an independent ethics committee or institutional review board at each study site prior to study commencement. The study was conducted in accordance with Good Clinical Practice and the Declaration of Helsinki, and registered at ClinicalTrials.gov (NCT00089791).
Assessments QCT scans of the left hip were performed at 120 kV with a pitch of 1 using 170 mAs, reconstructed using a 200 mm field of view, a slice thickness of 1 or 1.25 mm, and a medium kernel at baseline, and at months 12, 24, and 36. QCT technicians were trained on the techniques and procedures, including subject positioning and phantom calibration scanning. Scanner stability and cross-calibration were longitudinally assessed during the study. Scans were analyzed in a blindedto-treatment manner by a central laboratory (Synarc Inc., Newark, CA, USA) and analyzed using MIAF software. MIAF enables automated 3-dimensional segmentation of the hip, dividing the proximal femur into anatomical and compartment regions. In this study, the total hip volume of interest (VOI) was analyzed, which is approximately equivalent to the total hip region of interest with DXA. The QCT total hip integral VOI was segmented into trabecular, subcortical, and cortical bone compartments (Fig. 1). The periosteal and endosteal surfaces defining the cortical compartment were segmented as described previously [27]. Then the trabecular compartment was obtained by a homogeneous 2 mm peeling process from the endosteal surface. The selection of 2 mm peeling was based on phantom measurements to account for blurring artifacts introduced by the limited spatial resolution of the CT scanner. The peeled volume was denoted as the subcortical compartment and represents the transitional zone between compact cortex and pure trabecular bone, a region that is thought in this age group to correspond to cortical bone, which has been “trabecularized” through endocortical and intracortical resorption. To further explore the changes within the cortex, the segmented cortical compartment was electronically partitioned into an outer and an inner cortex, where the outer cortex covered two-thirds and the inner cortex covered one-third of the total cortical thickness. For each compartment, vBMD and volume were measured and BMC calculated from the product of vBMD and volume. To evaluate the consistency between QCT and DXA, changes at the total hip using scans from Hologic, Inc. (Bedford, MA, USA; n = 57) or GE Healthcare Lunar (Waukesha, WI, USA; n = 5) DXA machines available from the subjects in the QCT study also were compared at baseline and months 12, 24, and 36.
484
H.K. Genant et al. / Bone 56 (2013) 482–488 Table 1 Baseline characteristics. Placebo N = 26 Age (years) Ethnicity (n, %) White/Caucasian Black/African–American Hispanic/Latino BMI (kg/m2) Creatinine clearance (mL/min) Total hip integral vBMD (mg/cm3) Total hip aBMD (g/cm2) Total hip BMD T-score Total hip BMC (mg)
Denosumab N = 36
74.2 (6.1)
72.8 (4.7)
14 (53.8) 1 (3.8) 11 (42.3) 25.0 (3.9) 60.5 (21.0) 216 (31) 0.70 (0.1) −2.1 (0.7) 15603 (3102)
22 (61.1) 0 14 (38.9) 26.0 (4.9) 64.3 (21.0) 224 (34) 0.74 (0.1) −1.7 (0.9) 16843 (2664)
Values are means (standard deviations) unless otherwise indicated. aBMD, areal bone mineral density; BMI, body mass index; BMC, bone mineral content; BMD, bone mineral density; vBMD, volumetric bone mineral density.
Fig. 1. Hip QCT regions of interest with MIAF software. Trabecular (red), subcortical (yellow), and cortical (blue) compartments of the total hip volume of interest analyzed with MIAF software. The total hip volume of interest includes the neck, trochanter, and intertrochanter. MIAF, Medical Image Analysis Framework; QCT, quantitative computed tomography.
Study endpoints Endpoints for this substudy included changes in total hip integral, trabecular, subcortical, and cortical vBMD and BMC from baseline and compared with placebo at months 12, 24, and 36. In addition, the outer and inner cortex regions were assessed. Statistical analysis Subjects had to have a baseline scan and ≥1 post-baseline scan analyzed by MIAF to be included in the analysis. Hip QCT scans at each annual visit for each subject were included in the analyses. There was no imputation of missing data. The percentage and absolute changes from baseline for vBMD and BMC were determined. Data analyses assessed changes over time relative to baseline for each treatment group and also compared with placebo. The percentage and absolute changes from baseline were analyzed using an analysis of covariance (ANCOVA) model including treatment and adjusting for baseline value and age strata (stratification factor). Least-squares means and 95% confidence intervals (CIs) for each treatment and for the treatment difference (denosumab — placebo) at each time point were generated. All analyses were exploratory and post hoc. P-values and CIs were not adjusted for multiplicity. Results This substudy included 62 postmenopausal women with osteoporosis (placebo N = 26; denosumab N = 36). Subject demographics were balanced between treatment groups (Table 1). Most women were
White/Caucasian (53.8% placebo; 61.1% denosumab), with a mean age of 74.2 years in the placebo group and 72.8 years in the denosumab group. Mean total hip integral vBMD was 216 mg/cm3 and 224 mg/cm3 for the placebo and denosumab groups, respectively, and mean total hip aBMD was 0.70 g/cm2 for the placebo group and 0.74 g/cm2 for the denosumab group. Mean total hip integral BMC as measured by QCT was 15603 mg and 16843 mg for the placebo and denosumab groups, respectively. At baseline, the proportion that each compartment contributed to BMC was 69% for the cortical compartment, 18% for the trabecular compartment, and 13% for the subcortical compartment. These proportions were similar within each treatment group, and remained consistent at month 36. Using QCT MIAF, denosumab treatment was shown to significantly increase total hip integral vBMD from baseline and compared with placebo at months 12, 24, and 36. In the denosumab group, the mean percentage change from baseline to month 36 in total hip integral vBMD was 6.4% (p b 0.0001; Fig. 2). In the placebo group, total hip integral vBMD decreased over the same time interval by − 1.5% (p = 0.008). The treatment difference between denosumab and placebo was significant at months 12, 24, and 36 (p b 0.01 for all). Integral volume of the total hip did not significantly change in either group (data not shown). The BMD results were similar when assessed by DXA (Fig. 2). At baseline, total hip integral vBMD and aBMD for all subjects showed a strong correlation (r = 0.83; p b 0.0001; data not shown). Changes in vBMD and aBMD during the study were moderately correlated in both the placebo group (r = 0.47; p b 0.0001) and the denosumab group (r = 0.32; p = 0.0004). The percentage gains in total hip integral vBMD in the denosumab group were accounted for by significant increases in the trabecular, subcortical, and cortical compartments at months 12, 24, and 36 (Fig. 3). Within the cortical compartment, similar improvements were observed in the outer and inner cortical regions (data not shown). Denosumab treatment also significantly increased total hip integral BMC from baseline by month 12 (2.4%; p b 0.001), and the improvement progressed over 36 months. Treatment with denosumab resulted in a mean percentage change from baseline to month 36 in total hip integral BMC of 4.8% (p b 0.0001), and treatment with placebo led to a decrease of −2.6% over the same time interval (p = 0.0004; Fig. 4). The treatment difference between denosumab and placebo was significant at months 12, 24, and 36 (p b 0.001 for all). Similar to observations with total hip integral vBMD, a strong correlation also was observed at baseline for these QCT MIAF total integral BMC measurements and DXA BMC for all subjects (r = 0.88; p b 0.0001; data not shown). Significant percentage gains in BMC from baseline and compared with placebo also were observed in the denosumab group in each bone compartment, specifically the trabecular, subcortical, and cortical
H.K. Genant et al. / Bone 56 (2013) 482–488
485
Fig. 2. Integral BMD percentage changes from baseline assessed by QCT MIAF and DXA at the total hip. Least-squares means, 95% confidence intervals (CIs), and p-values from analysis of covariance model are presented. ⁎p ≤ 0.002 compared with baseline and placebo; †p b 0.05 compared with baseline; ‡p b 0.05 compared with month 12. Month 12, n = 60; month 24, n = 59; month 36, n = 62. aBMD, areal bone mineral density; DXA, dual-energy x-ray absorptiometry; MIAF, Medical Image Analysis Framework; QCT, quantitative computed tomography; vBMD, volumetric bone mineral density.
compartments. In the denosumab group at month 12, BMC increased by 4.1% in the trabecular compartment, 2.3% in the subcortical compartment, and 2.2% in the cortical compartment (p b 0.001 for all). Gains also were observed in all 3 compartments at month 24 (7.2%, 3.9%, and 3.2%, respectively; p b 0.05 for all) and month 36 (8.4%, 4.9%, and 3.9%, respectively; p b 0.001 for all; Fig. 4). Outer and inner cortical regions also had significant gains from baseline and placebo (data not shown). Observed absolute changes in vBMD and BMC for integral and compartmental assessments also were significant in the denosumab group compared with the placebo group (p b 0.0001 for all), with larger absolute changes in the cortical compartment than the trabecular or subcortical compartments (Figs. 4A and B). The absolute increases from baseline observed in hip BMC at month 36 were 247 mg in the trabecular compartment, 108 mg in the subcortical compartment, and 456 mg in the cortical compartment in the denosumab-treated group. Discussion
Fig. 3. QCT MIAF vBMD percentage changes from baseline in total hip compartments. A. Trabecular compartment. B. Subcortical compartment. C. Cortical compartment. Least-squares means, 95% confidence intervals (CIs), and p-values from analysis of covariance model are presented. ⁎p b 0.05 compared with baseline and placebo; †p b 0.05 compared with baseline; ‡p b 0.0001 compared with month 12. Month 12, n = 60; month 24, n = 59; month 36, n = 62. MIAF, Medical Image Analysis Framework; QCT, quantitative computed tomography; vBMD, volumetric bone mineral density.
We undertook this analysis to further characterize compartmental changes associated with the observed improvements in aBMD previously documented by DXA with denosumab treatment at the total hip, in the context of the significant hip fracture reductions observed in the FREEDOM study [20]. MIAF provides a more comprehensive method to evaluate integral and compartment changes from QCT scans, including measuring changes within subregions of the cortex, evaluating the subcortical region, and quantifying cortical geometry. In this QCT MIAF substudy from FREEDOM, significant and progressive increases in total hip integral vBMD and BMC were confirmed to result from significant corresponding gains across trabecular and cortical compartments at months 12, 24, and 36. The results extend the previously observed aBMD increases from other phase 2 and phase 3 denosumab clinical trials that have measured bone mass using DXA [18–21]. The positive effect of denosumab on total hip integral vBMD and BMC is consistent with a recently reported study using MINDWAYS to analyze QCT scans [25]. However, results for the cortical compartment differ as the MINDWAYS analysis showed large increases with denosumab in cortical BMC and volume, but surprisingly not in cortical BMD, suggesting that the increase in BMC was largely caused by an increase in cortical volume [25]. The MIAF analysis showed similar percentage changes for vBMD and BMC across all bone compartments indicating that volumes, in particular cortical volume, did not change substantially. This difference with respect to the MINDWAYS analysis is explained by the difference in segmentation approaches. Indeed, simulations explained that with a global threshold, as used by MINDWAYS,
486
H.K. Genant et al. / Bone 56 (2013) 482–488
A. vBMD (mg/cm3) Percentage
Absolute Change
15
Denosumab 40
9.9%*
29*
al
Su
ab Tr
213 230
tic
ta To 229 247
Su
Tr 74 86
0
–3
l
al
–5†
tic
bc
–3†
522 551
C or
or
ec ab
–10
al tic
ar ul
ta To
0 –5
–15
Actual Values (mg/cm3) Placebo 229 Denosumab 247
5
C or
–7.8%†
7*
10
al
–10
14*
tic
−1.7%
15*
15
or
0% † –5 –1.5%
20
bc
0
25
ar
5.5%*
ul
6.4%*
5
30
ec
6.4%*
Absolute Change From Baseline (mg/cm3)
35
10
l
Percentage Change From Baseline
Placebo
74 86
213 230
522 551
B. BMC (mg) Percentage
Absolute Change Placebo
Denosumab
10 4.9%*
4.8%*
3.9%*
5
0 –1.1%
†
–5 –2.6%
–3.1%†
–10 –9.0%†
–15
Absolute Change From Baseline (mg)
1200 8.4%*
812*
1000 800
456*
600 400
247* 108*
200 0 –60†
–200
–78
–207†
–400
2857 3311
al
al C
or
tic
tic Su
bc or
ul Tr
ab ec
or C
bc or Su 2092 2259
ar
ta To 15977 17135
l
al
al
11030 11564
tic
ar 2857 3311
tic
Actual Values (mg) Placebo 15977 Denosumab 17135
ul
To
ta
l
–600 –346†
Tr ab ec
Percentage Change From Baseline
15
2092 2259
11030 11564
Fig. 4. QCT MIAF percentage and absolute changes in hip vBMD and BMC at month 36. A. vBMD (mg/cm3). B. BMC (mg). Least-squares means, 95% confidence intervals (CIs), and p-value from analysis of covariance model are presented. ⁎p b 0.0001 compared with both baseline and placebo; †p b 0.05 compared with baseline. Month 12, n = 60; month 24, n = 59; month 36, n = 62. BMC, bone mineral content; MIAF, Medical Image Analysis Framework; QCT, quantitative computed tomography; vBMD, volumetric bone mineral density.
a longitudinal change in cortical BMD resulted in an artificial change in cortical volume, and therefore an exaggeration of the change in cortical BMC relative to the change in cortical BMD. Gains also were observed in the subcortical (transitional) compartment, a region also relevant to bone strength, and which may represent remnants of eroded cortical bone, the trabecular–cortical boundary, and/or cortical bone that has become “trabecularized” from endocortical and intracortical resorption. The absolute changes in cortical vBMD and BMC in subjects treated with denosumab were noteworthy and larger than those observed in the trabecular compartment. While both increases in trabecular and cortical vBMD and BMC are important to improve bone strength, the large gain in the cortical region, which was similar in the outer and inner regions of the cortical
shell, is of particular significance to older patients with osteoporosis who may have already lost substantial trabecular bone, or in whom the trabecular structures in the bone have become disconnected, and are at increased risk for fracture. In these individuals, their higher fracture risk and decreased hip strength have been attributed to significant deficits in the cortical shell [28–30]. Thus, protecting and improving the cortical compartment may be paramount to observe fracture reduction in the elderly population. Supporting this observation is the report that denosumab significantly reduced the risk of hip fractures in subjects aged ≥75 years by 62% (95% CI, 22%, 82%). This observed hip fracture incidence in the denosumab-treated older subjects was similar to that of untreated subjects b75 years in whom hip fractures are a less frequent event [31].
H.K. Genant et al. / Bone 56 (2013) 482–488
The data reported here therefore provide more accurate insight on the effects of denosumab on trabecular, subcortical, and cortical bone compartments, and the possible relationships to fracture reductions. In FREEDOM, improvements in total hip aBMD observed with denosumab treatment accounted for approximately 80% of the nonvertebral fracture risk reduction [24], and this robust relationship suggested that the gains in mass with denosumab treatment were achieved across all compartments, a hypothesis now documented in this study. This study also highlights the value of evaluating absolute change, in addition to percentage change, when documenting changes over time with QCT. Indeed, previous reporting of percentage change rather than absolute change may have obscured our understanding of the impact of therapies on different bone compartments and their possible contributions to fracture risk reductions. Percentage changes in both vBMD and BMC in the denosumab-treated subjects were larger in the trabecular compartment than in the cortical compartment, but assessment of absolute changes revealed that larger gains in vBMD and BMC were observed in the cortical compartment. The absolute increases in vBMD and BMC were also noteworthy in the subcortical compartment, particularly because those increases occurred in a significantly smaller subcortical volume compared with the trabecular and cortical volumes. The apparent discrepancy between percentage and absolute changes is explained by the fact that vBMD in the trabecular compartment is lower because of the large inter-trabecular spaces and the low density of the surrounding fatty bone marrow. While it is informative to differentiate percentage and absolute changes, as well as vBMD and BMC changes, it remains to be determined, which has the greatest influence on biomechanical strength. Nevertheless, this study supports the use of techniques other than DXA in the evaluation of changes in response to therapy to better understand their impact on fracture risk reductions. There are recognized technical limitations of the QCT technique, in particular partial volume artifacts in the cortical regions, which are caused by the limited spatial resolution of about 500 μm in-plane and 1 to 1.25 mm slice thickness, and overall beam hardening effects, which can influence the measurements [32]. The analysis also is limited by the small numbers of subjects, although QCT studies reporting on the effect of other therapies have been typically of this size or smaller [33–35]. Finally, as QCT was only performed in a subset of FREEDOM participants, it is not possible to relate QCT changes to fracture events in the overall FREEDOM study, and results of sub-VOIs of the total hip, such as femoral neck, trochanter, or intertrochanter within the total hip, were not detailed in this study. Notwithstanding these limitations, this study advances our understanding of bone compartmental changes in response to denosumab treatment and their potential contributions to observed improved strength, which was previously reported for the same subset of subjects [36], and to the robust hip fracture reductions observed in FREEDOM in those patients at increased or high risk for fracture [20]. Conclusion Denosumab treatment was associated with progressive improvements in bone density and mass at the hip over the 36-month duration of the FREEDOM study. These improvements were documented in the trabecular, subcortical, and cortical compartments. Denosumab offers a valuable therapeutic option to significantly increase bone mass at the hip to reduce hip fracture risk in postmenopausal women with osteoporosis at increased or high risk for fracture. Role of the funding source This study was funded by Amgen Inc. Amgen employees (HR and CL) contributed to the design of the study, assisted in reviewing and interpreting the results, and writing this manuscript.
487
Conflict of interest HKG: Consultant to Amgen Inc., Lilly, Merck, Novartis, Pfizer, Radius, Roche, GSK, BMS, Janssen, ONO, and Servier, and stock in Synarc. KE: Employee of and stock options in Synarc. JRZ: Consultant and/or speaker for Amgen Inc., Eli Lilly, GSK, and Merck. AH: Speaker for Amgen Inc., Eli Lilly, Merck, and Novartis. CKY: Research grant support from Amgen Inc., Bayer, Eli Lilly, Merck, Novartis, Pfizer, and P&G, and is a consultant and/or speaker for Amgen Inc., Merck, and Pfizer. SS: No conflicts of interest. MAB: Consultant to Amgen Inc., Lilly, and Warner Chilcott. EF: Speaker for Amgen Inc., Eli Lilly, Merck, and Servier. TF: Employee of and stock options in Synarc. MM: Speaker and/or consultant for Amgen Inc., Lilly, Merck, Novartis, and Warner Chilcott. CL and HR: Employees of and/or stock options in Amgen Inc.
Acknowledgments The authors wish to thank Mandy Suggitt and Erica Rockabrand, PhD, of Amgen Inc. for editorial assistance, coordination of authors' input, and figure preparation, and Andrea Wang of Amgen Inc. for statistical analysis assistance.
References [1] Bouxsein ML. Technology insight: noninvasive assessment of bone strength in osteoporosis. Nat Clin Pract Rheumatol 2008;4:310–8. [2] Genant HK, Engelke K, Fuerst T, Gluer CC, Grampp S, Harris ST, et al. Noninvasive assessment of bone mineral and structure: state of the art. J Bone Miner Res 1996;11: 707–30. [3] Carballido-Gamio J, Harnish R, Saeed I, Streeper T, Sigurdsson S, Amin S, et al. Proximal femoral density distribution and structure in relation to age and hip fracture risk in women. J Bone Miner Res 2013;28:537–46. [4] Christiansen BA, Kopperdahl DL, Kiel DP, Keaveny TM, Bouxsein ML. Mechanical contributions of the cortical and trabecular compartments contribute to differences in age-related changes in vertebral body strength in men and women assessed by QCT-based finite element analysis. J Bone Miner Res 2011;26:974–83. [5] Kim KM, Brown JK, Kim KJ, Choi HS, Kim HN, Rhee Y, et al. Differences in femoral neck geometry associated with age and ethnicity. Osteoporos Int 2011;22:2165–74. [6] Sornay-Rendu E, Cabrera-Bravo JL, Boutroy S, Munoz F, Delmas PD. Severity of vertebral fractures is associated with alterations of cortical architecture in postmenopausal women. J Bone Miner Res 2009;24:737–43. [7] Ammann P, Rizzoli R. Bone strength and its determinants. Osteoporos Int 2003;14 (Suppl. 3):S13–8. [8] Brandi ML. Microarchitecture, the key to bone quality. Rheumatology (Oxford) 2009;48 (Suppl. 4):iv3–8. [9] Steiniche T, Christiansen P, Vesterby A, Hasling C, Ullerup R, Mosekilde L, et al. Marked changes in iliac crest bone structure in postmenopausal osteoporotic patients without any signs of disturbed bone remodeling or balance. Bone 1994;15:73–9. [10] Tobias JH. How do bisphosphonates prevent fractures? Ann Rheum Dis 1997;56: 510–1. [11] Genant HK, Cann CE, Ettinger B, Gordan GS, Kolb FO, Reiser U, et al. Quantitative computed tomography for spinal mineral assessment: current status. J Comput Assist Tomogr 1985;9:602–4. [12] Lacey DL, Tan HL, Lu J, Kaufman S, Van G, Qiu W, et al. Osteoprotegerin ligand modulates murine osteoclast survival in vitro and in vivo. Am J Pathol 2000;157:435–48. [13] Lacey DL, Timms E, Tan HL, Kelley MJ, Dunstan CR, Burgess T, et al. Osteoprotegerin ligand is a cytokine that regulates osteoclast differentiation and activation. Cell 1998;93:165–76. [14] Udagawa N, Takahashi N, Yasuda H, Mizuno A, Itoh K, Ueno Y, et al. Osteoprotegerin produced by osteoblasts is an important regulator in osteoclast development and function. Endocrinology 2000;141:3478–84. [15] Yasuda H, Shima N, Nakagawa N, Yamaguchi K, Kinosaki M, Mochizuki S, et al. Osteoclast differentiation factor is a ligand for osteoprotegerin/osteoclastogenesisinhibitory factor and is identical to TRANCE/RANKL. Proc Natl Acad Sci U S A 1998;95:3597–602. [16] Baron R, Ferrari S, Russell RG. Denosumab and bisphosphonates: different mechanisms of action and effects. Bone 2011;48:677–92. [17] Bekker PJ, Holloway DL, Rasmussen AS, Murphy R, Martin SW, Leese PT, et al. A single-dose placebo-controlled study of AMG 162, a fully human monoclonal antibody to RANKL, in postmenopausal women. J Bone Miner Res 2004;19:1059–66. [18] Bone HG, Bolognese MA, Yuen CK, Kendler DL, Wang H, Liu Y, et al. Effects of denosumab on bone mineral density and bone turnover in postmenopausal women. J Clin Endocrinol Metab 2008;93:2149–57. [19] Brown JP, Prince RL, Deal C, Recker RR, Kiel DP, de Gregorio LH, et al. Comparison of the effect of denosumab and alendronate on BMD and biochemical markers of bone turnover in postmenopausal women with low bone mass: a randomized, blinded, phase 3 trial. J Bone Miner Res 2009;24:153–61.
488
H.K. Genant et al. / Bone 56 (2013) 482–488
[20] Cummings SR, San Martin J, McClung MR, Siris ES, Eastell R, Reid IR, et al. Denosumab for prevention of fractures in postmenopausal women with osteoporosis. N Engl J Med 2009;361:756–65. [21] Lewiecki EM, Miller PD, McClung MR, Cohen SB, Bolognese MA, Liu Y, et al. Two-year treatment with denosumab (AMG 162) in a randomized phase 2 study of postmenopausal women with low BMD. J Bone Miner Res 2007;22:1832–41. [22] McClung MR, Lewiecki EM, Cohen SB, Bolognese MA, Woodson GC, Moffett AH, et al. Denosumab in postmenopausal women with low bone mineral density. N Engl J Med 2006;354:821–31. [23] Miller PD, Bolognese MA, Lewiecki EM, McClung MR, Ding B, Austin M, et al. Effect of denosumab on bone density and turnover in postmenopausal women with low bone mass after long-term continued, discontinued, and restarting of therapy: a randomized blinded phase 2 clinical trial. Bone 2008;43:222–9. [24] Austin M, Yang YC, Vittinghoff E, Adami S, Boonen S, Bauer DC, et al. Relationship between bone mineral density changes with denosumab treatment and risk reduction for vertebral and nonvertebral fractures. J Bone Miner Res 2012;27:687–93. [25] McClung MR, Zanchetta JR, Hoiseth A, Kendler DL, Yuen CK, Brown JP, et al. Denosumab densitometric changes assessed by quantitative computed tomography at the spine and hip in postmenopausal women with osteoporosis. J Clin Densitom 2013;16:250–6. [26] Bousson V, Le Bras A, Roqueplan F, Kang Y, Mitton D, Kolta S, et al. Volumetric quantitative computed tomography of the proximal femur: relationships linking geometric and densitometric variables to bone strength. Role for compact bone. Osteoporos Int 2006;17:855–64. [27] Kang Y, Engelke K, Kalender WA. A new accurate and precise 3-D segmentation method for skeletal structures in volumetric CT data. IEEE Trans Med Imaging 2003;22:586–98.
[28] Donaldson LJ, Cook A, Thomson RG. Incidence of fractures in a geographically defined population. J Epidemiol Community Health 1990;44:241–5. [29] Kanis JA, Johnell O, Oden A, Dawson A, De Laet C, Jonsson B. Ten year probabilities of osteoporotic fractures according to BMD and diagnostic thresholds. Osteoporos Int 2001;12:989–95. [30] Poole KE, Treece GM, Ridgway GR, Mayhew PM, Borggrefe J, Gee AH. Targeted regeneration of bone in the osteoporotic human femur. PLoS One 2011;6:e16190. [31] Boonen S, Adachi JD, Man Z, Cummings SR, Lippuner K, Torring O, et al. Treatment with denosumab reduces the incidence of new vertebral and hip fractures in postmenopausal women at high risk. J Clin Endocrinol Metab 2011;96:1727–36. [32] Genant HK, Engelke K, Hanley DA, Brown JP, Omizo M, Bone HG, et al. Denosumab improves density and strength parameters as measured by QCT of the radius in postmenopausal women with low bone mineral density. Bone 2010;47:131–9. [33] Burghardt AJ, Kazakia GJ, Sode M, de Papp AE, Link TM, Majumdar S. A longitudinal HR-pQCT study of alendronate treatment in postmenopausal women with low bone density: Relations among density, cortical and trabecular microarchitecture, biomechanics, and bone turnover. J Bone Miner Res 2010;25:2558–71. [34] Engelke K, Fuerst T, Dasic G, Davies RY, Genant HK. Regional distribution of spine and hip QCT BMD responses after one year of once-monthly ibandronate in postmenopausal osteoporosis. Bone 2010;46:1626–32. [35] Rizzoli R, Chapurlat RD, Laroche JM, Krieg MA, Thomas T, Frieling I, et al. Effects of strontium ranelate and alendronate on bone microstructure in women with osteoporosis. Results of a 2-year study. Osteoporos Int 2012;23:305–15. [36] Keaveny TM, McClung M, Genant HK, Zanchetta JR, Kendler DL, Brown JP, et al. Denosumab improves both femoral and vertebral strength in women with osteoporosis: results from the FREEDOM trial. J Bone Miner Res 2010;25:S31.
