Long-Term TNFi Treatment for AxSpA Improved, Maintained Bone Mineral Density

In patients with radiographic axial spondyloarthritis (axSpA), lumbar spine bone mineral density (BMD) improved significantly and was maintained during long-term tumor necrosis factor inhibitor (TNFi) treatment, according to a study published in Seminars in Arthritis and Rheumatism.¹

Axial spondyloarthritis, a chronic rheumatic disease that causes inflammation of the spine and sacroiliac joint, is associated with lower quality of life, higher mortality, and substantial cost burden for patients.² It impacts up to 1.4% of adults in the US, although diagnosis can be difficult.

Due to the inflammation present with axial spondyloarthritis, there is increased bone metabolism in the axial skeleton, and osteopenia can be seen even in early stages of axial spondyloarthritis.¹ The bone resorption seen in axial spondyloarthritis is faster paced than typical age-related resorption. With decreased BMD comes a higher risk of vertebral fractures (VFs) among patients with axial spondyloarthritis. VFs also often go without clinical attention because they are difficult to recognize in axial spondyloarthritis, which is characterized by back pain and spine damage.

Findings suggest checking regular radiographs in clinical practice for loss of bone density or VFs can be helpful in managing axial spondyloarthritis. - Mutshino_Artwork - stock.adobe.com

Research has shown treatment with TNFIs to improve lumbar spine BMD within 6 months of therapy initiation with continued improvement through 3 years of treatment.³ However, longer term data assessing BMD and development of progression of VFs over time with TNFi treatment are lacking, the study authors noted.¹ Therefore, they analyzed BMD and radiographic VF development throughout 8 years of TNFi treatment in patients with axial spondyloarthritis.

The study population included 126 patients participating in the Groningen Leeuwarden Axial SpA (GLAS) cohort who initiated TNFi treatment from October 2004 to December 2014 and had at least 8 years of follow-up data available. Of these patients, 97% had radiographic axSpA. The mean patient age was 41.5 years, median symptom duration was 14 years, and most patients (75%) were male.

Baseline characteristics were similar among patients with and without BMD measurements or radiographs to assess VFs, and patients who received anti-osteoporotic therapy were excluded from the study. Overall, the median lumbar spine BMD Z-score was –0.5 (IQR, –1.4-0.7), and 20% of patients had radiographic VFs at baseline.

Compared with baseline, the median percentage of improvement in lumbar spine BMD Z-score was 8.9% (2.8-15.8) at 4 years and 7.2% (2.2-14.7) after 8 years. BMD Z-scores significantly improved at follow-up vs baseline, with significant improvements seen up to and at 4 years in the lumbar spine, as well as 2 years in the hip. Afterward, BMD remained stable. Markers of disease activity, including mean Ankylosing Spondylitis Disease Activity Score (ASDAS) and median (Bath Ankylosing Spondylitis Disease Activity Index ) BASDAI measurements, also improved quickly and were maintained. The mean change in ASDAS was 1.7, and the mean change in BASDAI was 2.4 at 8 years vs baseline.

New VFs developed in 14 (16%) of 90 patients who had baseline and 8-year radiographs available, and existing VFs grew more severe in 5 (6%) patients with available data. A total of 44 VFs were present at 8 years, with 30% being grade 2 or 3. All except 3 fractures were in the middle or lower thoracic spine.

While the results cannot be generalized to early axial spondyloarthritis or non-radiographic disease, the findings suggest checking regular radiographs in clinical practice to assess loss of bone density or VFs can be helpful in managing axSpA.

“Radiographic VFs seem to continue to develop and progress, irrespective of improvement in BMD,” the authors wrote. “Therefore, clinical attention for loss of bone density of the spongy bone and the occurrence of vertebral fractures is important.”

References

1. Siderius M, Wink F, Kieskamp S, et al. Improvement of bone mineral density and new vertebral fractures during 8 years of TNF-α inhibition in patients with axial spondyloarthritis. Semin Arthritis Rheum. Published online July 11, 2024. doi:10.1016/j.semarthrit.2024.152523

2. Walsh JA, Magrey M. Clinical manifestations and diagnosis of axial spondyloarthritis. J Clin Rheumatol. 2021;27(8):e547-e560. doi:10.1097/RHU.0000000000001575

3. Arends S, Spoorenberg A, Houtman PM, et al. The effect of three years of TNFα blocking therapy on markers of bone turnover and their predictive value for treatment discontinuation in patients with ankylosing spondylitis: a prospective longitudinal observational cohort study. Arthritis Res Ther. 2012;14(2):R98. doi:10.1186/ar3823