Use of MRI to Evaluate Patients on Infliximab Therapy

Dr. Norman B. Gaylis

USE OF IN-OFFICE MRI IN THE EVALUATION OF PATIENTS WITH RHEUMATOID

Objectives: To assess the performance of an in-office magnetic resonance imaging (MRI) system in the diagnosis of rheumatoid arthritis (RA) while evaluating the treatment benefit with the anti-TNF-alpha agent infliximab.

Methods: Fourteen patients who satisfy the American College of Rheumatology criteria for the diagnosis of RA were evaluated in a single rheumatology practice with a portable MRI system (MagneVu 1000, Carlsbad, Ca, USA). This self-shielded low field (0.2-Tesla) scanner operates on standard (USA) 110-volt power supply and occupies ordinary office space. MR imaging capabilities of the system include high resolution, thin-section (0.6–1 mm), 3-dimensional multi-echo data acquisition; T1 and T2 weighted spin echo, and short tau inversion recovery (STIR) sequences. Patients were imaged at baseline and scheduled for follow-up MRI at 6 months. A board-certified musculoskeletal radiologist interpreted the MRI results but remained independent of the patient’s clinical treatment and outcome. Bone erosions were defined as a sharply marginated juxta-articular bone defect with extension through the adjacent cortex. Signal characteristics for erosion were low signal intensity with respect to marrow fat on T1 weighted images and high signal intensity on STIR images. All 14 patients received intravenous infliximab (Centocor, Malvern, Pa, USA) maintenance therapy with eleven patients (79%) also receiving concomitant methotrexate. Of these 14 patients, 86% had both wrists imaged (including all carpal bones and the 2nd and 3rd MCP joints) by T1 and STIR sequences while the remaining two patients had only one hand imaged.

The duration of infliximab treatment ranged from 5 months to 2 1/2 years. Dosing ranged from 3 to 7 mg/kg (median 4 mg/kg) with the infusion interval being approximately 7 weeks. Disease duration from time of presentation was <1 year in 10 patients (71%), less than 2 years in 1 patient (7%), and >2 years (maximum, 7 years) in 3 patients (21%). Seven patients were infused with infliximab within 2 years of diagnosis.

Results: Clinically, based on dose variations, all patients were perceived to have improved from baseline. Follow-up MRIs, (range, 5-8 months), reflected healing of erosions in 4 patients (29%), no change in 9 patients (64%), and an indeterminate result in 1 patient (7%). Of the 4 patients demonstrating erosion healing, time from initial RA diagnosis ranged from 9 months to 7 years and number of infliximab infusions from 5 to 14.

Conclusion: The results reflect that high-resolution in-office MRI is capable of demonstrating subtle changes in the morphology of erosions in RA patients undergoing active treatment and may be useful in providing a means of adjusting therapeutic and dosage requirements based on the progression of their erosive disease. Our results reflect no MRI measurable progression of erosive disease in patients on infliximab therapy and in addition the reversal of previously documented cortical erosions was noted in some patients. Inhibition of the progression of RA and the healing of joint damage may be possible in both patients with either early onset or longer-standing RA. These results support growing evidence that high-resolution in-office MRI may be beneficial in selecting the best biological modifier and optimal dose for each individual RA patient.

Click here for the Abstract presented at the European League Against Rheumatism, held in Berlin, Germany, in June 2004.