Impact of Tumor Necrosis Factor Inhibitor Versus Nonsteroidal Antiinflammatory Drug Treatment on Radiographic Progression in Early Ankylosing Spondylitis: Its Relationship to Inflammation Control During Treatment

OBJECTIVE: To investigate the impact of tumor necrosis factor inhibitor (TNFi) treatment and inflammation control on radiographic progression in early ankylosing spondylitis (AS) over 4 years. METHODS: We included a total of 215 patients with early AS (symptom duration <10 years) treated with TNFi (the TNFi group; n = 135) or with nonsteroidal antiinflammatory drugs (NSAIDs) (the control group; n = 80). Two blinded readers assessed radiographic progression using the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). Inflammation control was inferred from C‐reactive protein (CRP) levels time‐averaged between 2 radiologic assessments. Linear mixed modeling was used to estimate mSASSS changes over radiographic intervals as well as the impact of clinical factors on outcomes. RESULTS: The TNFi group had longer disease duration, a higher baseline CRP level, and a higher Bath Ankylosing Spondylitis Disease Activity Index than did controls. The time‐averaged CRP level over radiographic intervals was lower with TNFi treatment than with NSAID treatment (mean ± SD 0.27 ± 0.30 mg/dl versus 0.61 ± 0.68 mg/dl; P < 0.001). Overall, mean ± SD mSASSS change over the 2‐year interval was 1.30 ± 2.97 units. In the multivariable model adjusted for age, smoking status, baseline CRP level, and the presence of syndesmophytes at baseline, the TNFi group showed less mSASSS change over the 2‐year interval (β = −0.90 [95% confidence interval {95% CI} −1.51, −0.29]). However, when a time‐averaged CRP level was additionally included, it significantly influenced the mSASSS change (β = 1.02 [95% CI 0.32, 1.71]), decreasing the estimated group difference (β = −0.52 [95% CI −1.17, 0.14]). NSAID indices of both groups were not associated with either time‐averaged CRP levels or mSASSS changes. CONCLUSION: Effective suppression of inflammation by TNFi treatment decreases radiographic progression in early AS.