Background So far, inconsistent results have been reported regarding the effect of tumor necrosis factor-alpha (TNF-α) blocking therapy on radiographic progression in ankylosing spondylitis (AS).
Objectives To prospectively investigate spinal radiographic progression up to 6 years of TNF-α blocking therapy in patients with AS.
Methods Consecutive outpatients from the Groningen Leeuwarden AS (GLAS) cohort, fulfilling the modified New York criteria for AS, with available radiographs before start of TNF-α blocking therapy and after 2, 4, and/or 6 years of follow-up were included. Radiographs of the cervical and lumbar spine were scored by two independent readers using the modified Stoke AS Score (mSASSS). Readers were blinded for patient characteristics and time sequence of radiographs. Generalized estimating equations were used to analyze spinal radiographic progression and clinical assessments over time within subjects and to calculate mean radiographic progression rate at group level. Spinal radiographic progression was compared between patients with high (TNF-α blocker use of ≥80% of follow-up time) and low TNF-α blocker compliance and between patients with (presence of ≥1 syndesmophyte) and without definite radiographic damage at baseline.
Results 105 AS patients had mSASSS total scores available at baseline and after 2 years (n=81), 4 years (n=99) and/or 6 years (n=48) of follow-up. Of these patients, 73% were male, mean age was 42±11 years, median symptom duration was 16 years (range 1-47), 82% were HLA-B27 positive. Median baseline mSASSS was 12 (range 0-70) and 62 patients (59%) had definite radiographic damage at baseline.
Overall, spinal radiographic progression was linear with a mean progression rate of 0.66 mSASSS units/year. Radiographic progression was comparable between patients with high and low TNF-α blocker compliance (mean 0.64 vs. 0.68 mSASSS units/year, p=0.34). Radiographic progression was significantly higher in patients with than without definite radiographic damage at baseline (mean 1.04 vs. 0.26 mSASSS units/year, p<0.001). TNF-α blocking therapy resulted in a clear and sustained improvement in disease activity, physical function, and quality of life.
Conclusions This prospective longitudinal observational cohort study shows neither inhibition nor acceleration of radiographic progression over time at group level in AS patients who used TNF-α blocking therapy up to 6 years. Patients with no or limited spinal radiographic damage at baseline showed less radiographic progression compared to patients with more extensive radiographic damage. Whether early exposure to TNF-α blockers can halt radiographic progression remains to be demonstrated.
Acknowledgements The GLAS cohort was supported by an unrestricted grant from Pfizer. Pfizer had no role in the design, conduct, interpretation, or publication of this study.
Disclosure of Interest F. Maas: None declared, A. Spoorenberg Grant/research support: Abbott, Pfizer, Wyeth, Consultant for: Abbvie, Pfizer, UCB, E. Brouwer Grant/research support: Abbott, Pfizer, Wyeth, R. Bos Grant/research support: Pfizer, Consultant for: Pfizer, M. Efde: None declared, R. Chaudhry: None declared, N. Veeger: None declared, H. Bootsma: None declared, E. van der Veer: None declared, S. Arends Grant/research support: Abbott, Pfizer, Wyeth