The importance of absolute bone mineral density in the assessment of antiresorptive agents used for the prevention of osteoporotic fractures

Achieving osteoporosis treat-to-target goals with teriparatide or alendronate: sub-analysis of Japanese Osteoporosis Intervention Trial-05 (JOINT-05)

INTRODUCTION

The purpose of this study was to evaluate whether bone mineral density (BMD) ≥ -2.5 SD could be used as the treat-to-target (T2T) goal when treating osteoporosis with teriparatide (TPTD) and alendronate (ALN), and to investigate the relationship with incident vertebral fracture by re-analyzing data from a randomized, controlled trial (JOINT-05) involving postmenopausal Japanese women at high fracture risk.

MATERIALS AND METHODS

Participants received sequential therapy with once-weekly TPTD for 72 weeks, followed by ALN for 48 weeks (TPTD-ALN group) or ALN monotherapy for 120 weeks (ALN group). BMDs were measured at the lumbar spine (L2-4), total hip, and femoral neck at 0, 24, 48, 72, and 120 weeks by dual-energy X-ray absorptiometry. The T2T goal was BMD ≥ -2.5 SD, and the endpoint was the proportion of participants with baseline BMD < -2.5 SD in three measurement sites achieving BMD ≥ -2.5 SD.

RESULTS

A total of 559 participants were selected. BMD ≥ -2.5 SD at 120 weeks in the L2-4, total hip, and femoral neck sites was achieved in 20.5%, 23.1%, and 5.9%, respectively, in the TPTD-ALN group and 22.2%, 11.7%, and 7.3%, respectively, in the ALN group. Incident vertebral fractures occurred in areas of both lower and high BMD.

CONCLUSION

During the 1.5-year treatment period, more than 20% of participants achieved BMD ≥ -2.5 SD as a T2T goal at L2-4. Since the achievement level differed depending on the BMD measurement site, the appropriate site should be selected according to the baseline BMD level.

Impact of bone mineral density in reducing fracture risk in patients receiving alendronate plus alfacalcidol therapy

BACKGROUD

Changes in bone mineral density (BMD) are a potential surrogate marker for fracture endpoints in clinical trials. However little is known whether the increase in BMD in response to combination treatment with alendronate plus alfacalcidol is associated with fracture risk reduction. We aimed to evaluate the impact of BMD on fracture risk in osteoporosis patients, using the data from the randomized clinical trial comparing alendronate plus alfacalcidol with alendronate alone.

METHODS

We selected 412 patients with two or more prevalent vertebral fractures and who had BMD measurements at baseline and after 6, 12, and/or 24 months out of 2022 patients from the database of the Japanese Osteoporosis Intervention Trial. Patients in this subset who received combination treatment with alendronate plus alfacalcidol had shown a lower risk of fracture than patients treated with alendronate alone. We used Poisson regression model analysis to calculate the proportion of treatment effect (PTE) that was attributable to BMD increases in patients receiving combination treatment.

RESULTS

The highest PTE attributable to changes in BMD was 1.2% in patients with a BMD increase of 3% or more in the lumbar spine. For BMD measurements of the radius, the highest PTE was 2.8% with a BMD increase of 0% or more. For BMD measurements of the metacarpal bone, the highest PTE was 1.2% with a BMD increase of 3% or more. In patients with a BMD greater than or equal to 70% of the young adult mean in the lumbar spine, the PTE attributable to BMD was 0.2%. In patients with a BMD greater than or equal to 70% of the young adult mean in the radius, the PTE attributable to BMD was 0.3%.

CONCLUSIONS

The additional effects of alfacalcidol in reducing fracture risk do not likely result from increased BMD; other mechanisms remain a possibility.

Modeling and simulation of bone mineral density in Japanese osteoporosis patients treated with zoledronic acid using tartrate-resistant acid phosphatase 5b, a bone resorption marker

Annual intravenous administration of zoledronic acid is used in the treatment of osteoporosis. A mathematical model was developed to predict bone mineral density up to 2 years after two annual doses of zoledronic acid from the early values of a bone resorption marker in osteoporosis patients.

INTRODUCTION

The measurement of bone mineral density (BMD) has been used as a surrogate marker instead of the observation of incident fractures to detect the efficacy of treatment. However, this method requires a long time to obtain significant changes. On the other hand, bone resorption markers respond to bone resorption inhibitors within a few weeks. Therefore, the aim of this study was to develop a mathematical model predicting long-term BMD after two annual doses of zoledronic acid (ZOL) using the early response of a bone resorption marker in osteoporosis patients.

METHODS

The model was constructed using 3410 tartrate-resistant acid phosphatase 5b (TRACP-5b) serum concentrations and 1146 lumbar spine (L2-L4) BMD values from 306 patients with primary osteoporosis. A mathematical model was developed to describe the time-dependent profiles of TRACP-5b and BMD.

RESULTS

The percentage changes from baseline of the BMD (%BMD) at up to 2 years were predicted from patients' baseline BMD and baseline and 12-week TRACP-5b values by the model obtained. The simulated 90% prediction interval almost covered the observed %BMD distribution at each time point, and the predictions were comparable to the observed %BMD.

CONCLUSIONS

This is the first model to predict BMD for up to 2 years following two annual doses of ZOL using patients' background characteristics and the early response of TRACP-5b. This model allows us to inform patients at the initial stage of ZOL treatment of their predicted response to treatment.

24-Month Open-Label Teriparatide Once-Weekly Efficacy Research Trial Examining Bone Mineral Density in Subjects with Primary Osteoporosis and High Fracture Risk

Introduction

To clarify the additional efficacy and safety benefits of 24 months’ treatment with the once-weekly formulation of teriparatide, which is currently used for 72 weeks.

Methods

This was a multicenter, open-label, single-arm study conducted in Japan. Subjects who were 65 years or older with prevalent vertebral fractures received once-weekly subcutaneous injection of 56.5 μg teriparatide for 24 months. The main outcome measure was percentage change from baseline in lumbar (L2–L4) BMD measured by dual-energy X-ray absorptiometry.

Results

A total of 189 subjects received at least one dose of the once-weekly formulation of teriparatide. Lumbar, femoral neck, and total hip BMD increased significantly compared with baseline at Weeks 24, 48, 72, and 104. In addition, significant increases in lumbar (+1.5%) and femoral neck (+0.8%) BMD were noted at Week 104 compared with Week 72. Significant increases from baseline in BMD for radius 1/10 were noted at Weeks 24 and 104. No substantial increases were noted in the cumulative incidences of new vertebral fracture and other types of fracture after Week 72. The safety profile seen in the first 72 weeks remained unchanged until 104 weeks.

Conclusion

The once-weekly formulation of teriparatide is effective and safe for the treatment of osteoporosis over 24 months. The limitation of this study is that this was an open-label, single-arm study.

Funding: Asahi Kasei Pharma Corporation.

Clinical Trial Registration: JapicCTI-132276.

Treatment responses with once-weekly teriparatide therapy for osteoporosis

Monitoring bone mineral density is useful to assess treatment response for osteoporosis, but it does not always reflect fracture prevention. Two types of bone mineral density thresholds were used to analyze data from a once-weekly teriparatide trial, and they appear to be useful indicators of treatment success for osteoporosis.

INTRODUCTION

This study aimed to clarify whether the criteria of treatment response could be used to evaluate treatment success with once-weekly teriparatide.

METHODS

The data of subjects whose lumbar or femoral neck bone mineral density (BMD) was measured in the TOWER study were included. The least significant change (LSC) and the absolute change were used as the criteria for judgment of treatment success. The correlation between the incidence of fractures and the treatment response was also assessed.

RESULTS

There was no significant difference in baseline characteristics between the placebo and teriparatide groups. Once-weekly teriparatide therapy for 72 weeks showed treatment success in 79.2 % of the subjects for lumbar BMD and 44.1 % for femoral neck BMD by LSC and in 50.5 and 39.6 % by absolute change, respectively. A lower incidence of vertebral fracture was observed in patients who achieved treatment success for lumbar BMD. With the LSC, some treatment success was observed in the early phase of treatment, and it increased with treatment duration.

CONCLUSIONS

It appears that the LSC could be used as a surrogate efficacy indicator at an earlier stage of treatment, and the absolute criterion of -2.5SD was confirmed as a useful marker of long-term treatment success.

Bone strength and management of postmenopausal fracture risk with antiresorptive therapies: considerations for women's health practice

Bone strength – and, hence, fracture risk – reflects the structural and material properties of the skeleton, which changes with bone turnover during aging and following effective pharmacotherapy. A variety of powerful new techniques (quantitative computed tomography, as well as peripheral quantitative computed tomography and high-resolution peripheral quantitative computed tomography) provide precise images of bone structure and can be used to model the response of specific bones to different types of mechanical load. This review explores the various components of bone strength and the clinical significance of measures, such as bone mineral density, bone turnover markers, and modern imaging data, with regard to fracture risk in women with postmenopausal osteoporosis, before and after initiating antiresorptive therapy. These imaging and related techniques offer an ever-clearer picture of the changes in bone structure and bone mineral metabolism during normal aging and in osteoporosis, as well as in response to treatment. However, because the newer techniques are not yet available in routine practice, validated tools for absolute fracture risk assessment remain essential for clinical decision making. These tools, which are tailored to patient risk data in individual countries, are based on bone mineral density and other readily available clinical data. In addition, bone turnover marker measurements can be useful in assessing risk and guiding treatment decisions for women with postmenopausal osteoporosis. Such tests may be used before starting a patient on antiresorptive therapy and for ongoing monitoring of treatment effectiveness.