Radiation synovectomy using 188Re-tin colloid improves knee synovitis as shown by MRI in refractory rheumatoid arthritis

Background Radiation synovectomy is a useful local treatment for patients with refractory synovitis. We previously demonstrated the efficacy and safety of Re-188-tin colloid for treating rheumatoid arthritis patients with refractory knee synovitis. This open-label, prospective controlled study investigates magnetic resonance imaging (MRI) changes as well as clinical response in knees after receiving different radioactivities of intra-articular Re-188-tin colloid. Methods Sixteen patients with rheumatoid arthritis refractory to intra-articular corticosteroid therapy were treated with intra-articular injection of Re-188-tin colloid (555 MBq in six patients, 740 MBq in five, and 925 MBq in five). Contralateral knees were used as controls. efficacy and safety were evaluated 1, 3 and 6 months We compared the changes of synovial thickening and effusion between baseline and 6 months. Synovial thickness was measured by gadolinium-enhanced MRI. Results Pain intensities on a visual analogue scale were significantly lower (median pain reduction, 78.9%; P=0.0001), joint swelling improved (median, - 1.5; P=0.001), range of motion increased (median, 6 degrees, P=0.005), and joint tenderness decreased (median, - 1; P=0.005) in treated knees after 6 months. The control knees did not show any significant clinical improvement. At 6 months after therapy, synovial thickening of treated knees improved in 87.5% of patients (P<0.001), and synovial thicknesses were significantly decreased in treated knees (P=0.0067). Furthermore, reduction in synovial thickness was most noticeable in the group treated with 925 M Bq (P=0.007). No abnormalities in leukocyte or platelet counts, liver function tests, or urine analysis were observed. Conclusion Radiation synovectomy using Re-188-tin colloid in refractory rheumatoid arthritis patients improved MRI findings as well as clinical parameters.