INTRODUCTION: Magnetic resonance imaging (MRI) is increasingly used in patients with rheumatoid arthritis (RA) to determine residual inflammation after treatment and as a predictor of structural damage progression. Establishing an optimal threshold of inflammatory activity that predicts lower risk of structural damage progression may inform treatment decisions. This post hoc analysis investigated whether patients with RA at low risk of structural damage progression can be identified based on MRI inflammation thresholds.

METHODS: Hand and wrist MRI was performed at baseline, and at months 6 and 12 in a phase 3b, randomized, active-controlled, double-blind trial of abatacept in early RA (AVERT). Pathologies were scored using the OMERACT RA MRI Score. Data were stratified into two risk subgroups (less and more severe inflammation) for structural damage progression (erosion change > 0.5) based on baseline inflammation. In this post hoc analysis, log odds ratios of probability of progression {adjusted for baseline Disease Activity Score in 28 joints [C-reactive protein; DAS28 (CRP)]} were compared between subgroups to test the performance of inflammation thresholds.

RESULTS: There were 351 randomized and treated patients with baseline MRIs, of whom 276 (78.6%) and 235 (67.0%) had MRIs available at months 6 and 12, respectively. The DAS28 (CRP)-adjusted probabilities of progression from baseline to month 12 based on scores at baseline, and from months 6 to 12 based on month 6 scores, were significantly lower among patients with less inflammation (P < 0.0001-0.0459), independent of clinical disease activity. Predefined thresholds of synovitis ≤ 3 (total score 21), osteitis ≤ 3 (total score 69) and total inflammation score (osteitis double-weighted) ≤ 9 were associated with a lower likelihood of structural damage progression in unadjusted analyses.

CONCLUSION: Levels of MRI-determined inflammatory activity below defined thresholds were independently associated with a lower risk of structural damage progression in early RA, providing a potential trial endpoint for levels of inflammation not associated with progression.

TRIAL REGISTRATION: ClinicalTrials.gov identifier, NCT01142726.

FUNDING: Bristol-Myers Squibb.