FRI0642 USE OF MAGNETIC RESONANCE IMAGING FOR ASSESSMENT OF PATIENTS WITH IDIOPATHIC INFLAMMATORY MYOPATHIES – A SUBANALYSIS OF THE PROMETHEUS STUDY

Abstract

Background Prometheus study was a prospective, randomized, assessor-blind multicenter trial, conducted to evaluate the efficacy and safety of the combination therapy with methotrexate and glucocorticoids (GC) compared to GC treatment only in patients with polymyositis (PM) and dermatomyositis (DM). Muscle MRI has been used to assess disease activity and response to treatment. Objectives To assess MRI findings we developed new semi-quantitative scoring method and used it for activity assessment and evaluation of treatment effect after 3 months of therapy. Methods In a novel semi-quantitative assessment of edema, we used scoring 0, 1, 2, and 3 according to intensity of signal in each of the 16 thigh muscles. Muscle damage was evaluated in 3 basic thigh muscle compartments and pelvic muscles using Goutallier grading (0 – 5) based on extent of fatty replacement. Both sides were assessed, an average was made for each muscle, and values were summed up in the total score. Images were scored by 2 independent evaluators and the mean was used. Manual muscle test (MMT8) and creatinkinase (CK) were measured and patient’s global assessment (PGA), physician’s GA (PhGA) and muscle disease activity (MDA) were recorded on visual analogue scales. Results Seventeen patients had MR images taken before the baseline visit, 8 had also the second MRI after 3 months of therapy. There was a significant reduction of total MRI edema score (MRI ES) after 3 months in patients with PM and DM (from the mean 17.4 points, SD 13.7 to 8.0 points, SD 12.3; p=0.025). No significant progression of fatty atrophy was observed (from 16.0 points, SD 8.8, to 19.4, SD 4.6; p=0.3). At baseline, a significant correlation between MRI ES and PGA was noted (p=0.027). There was also a borderline association of MRI ES with muscle strength evaluated by MMT 8 (p=0.053). In a subset of 8 patients with longitudinally performed two MRI evaluations we found a good correlation between initial MRI edema score and the level of serum CK (p=0.028). However, no correlation was seen between the level of improvement in MRI ES and drop in CK or with any other clinical parameters after 3 months of treatment. The intensity of muscle edema at baseline was not predictive to improvement of any clinical parameters or CK, with a tendency to a better improvement of muscle disease activity in those who had higher MRI ES at baseline (corr. coeff. 0.445, p=0.073). Conclusion We proposed a new semi-quantitative scoring system for assessment of MR images in patients with PM and DM. This system was applied to record degree of muscle edema and fatty replacement in a subpopulation of patients treated in the Prometheus study. A significant reduction of MRI ES and no relevant progression of muscle atrophy and fatty replacement after 3 months of therapy was demonstrated. Initial MRI edema score correlated with some clinical and laboratory parameters (PGA, CK) but was not predictive to a degree of improvement during treatment. The results are limited by a small sample size, particularly in the subset with longitudinal MRI. Acknowledgement Supported by the project (Ministry of Health, Czech Republic) for conceptual development of research organization 00023728 (Institute of Rheumatology). Disclosure of Interests Kateřina Kubinova: None declared, Jiři Vencovský Consultant for: Samsung, Speakers bureau: AbbVie, Novartis, Pfizer, Sanofi, Eli Lilly, Biogen, UCB, MSD, Werfen, Roche