Reduction in Spinal Radiographic Progression in Ankylosing Spondylitis Patients Receiving Prolonged Treatment With Tumor Necrosis Factor Inhibitors

Objective To evaluate the course of spinal radiographic progression for up to 8 years of followup in a large cohort of ankylosing spondylitis (AS) patients treated with tumor necrosis factor (TNF) inhibitors. Methods Consecutive patients from the Groningen Leeuwarden AS cohort starting TNF inhibitors between 2004 and 2012 were included. Baseline and biannual radiographs were randomized with radiographs of TNF-naive AS patients and scored in chronologic order according to modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). The course of radiographic progression (linear or nonlinear) was investigated using generalized estimating equations. Primary analysis was performed in patients with complete data over 4, 6, and 8 years of followup. Sensitivity analysis was performed after single linear imputation of missing radiographic data and after adjusting for patient characteristics with possible influence on radiographic progression. Results At baseline, median mSASSS of 210 included AS patients was 2.8 (interquartile range 0.0–12.0), mean ± SD mSASSS 10.0 ± 15.5. During the first 4 years, radiographic progression followed a linear course (estimated mean progression rate was 1.7 for 0–2 and 2–4 years). A deflection from a linear course was found in patients with complete and imputed data over 6 and 8 years. The estimated mean 2-year progression rate reduced from 2.3 to 0.8 in patients with complete 8-year data. The same pattern was found after adjustment for baseline mSASSS scores, presence of syndesmophytes, sex, HLA–B27 status, age, symptom duration, smoking duration, body mass index, disease activity, and nonsteroidal antiinflammatory drug use. Conclusion This observational cohort study in AS patients receiving long-term TNF inhibitors showed a reduction in spinal radiographic progression after more than 4 years of followup.