The assessment of biologic treatment in patients with rheumatoid arthritis using FDG-PET/CT

Objectives. To evaluate whether there is a correlation between the differences in joint uptake of 2-[18F]-fluoro-2-deoxy-D-glucose (F-18-FDG) and the improvement of clinical findings in RA patients undergoing anti-TNF therapies. Methods. Twenty-two patients who received anti-TNF therapies, including infliximab for 16 patients and etanercept for 6 patients, were assessed. PET with F-18-FDG studies and clinical assessments were performed at baseline and 6 months after the initiation of therapy. The maximal standardized uptake value (SUVmax) was used as a representative value for the assessment of the FDG uptake in the bilateral shoulder, elbow, wrist, hip, knee and ankle joints. Spearman's rank correlation test was applied to assess the correlation between the SUV and the clinical parameters. Results. The delta SUV (12 joints), the difference in the SUVmax of the affected 12 joints before and after treatment, was positively correlated with the delta DAS28 (r = 0.609, P = 0.003), delta DAS28-CRP (r = 0.656, P = 0.001) and delta tender joint count (TJC) (r = 0.609, P = 0.003). There were also significantly positive correlations between delta SUV (8 joints); the difference in the SUVmax of the bilateral shoulder, elbow, wrist and knee joints before and after treatment and the delta DAS28 (r = 0.642, P = 0.001), delta DAS28-CRP (r = 0.712, P < 0.001) and delta TJC (r = 0.608, P = 0.003), respectively. Conclusion. The FDG uptake observed in the inflamed RA joints may reflect disease activity. The FDG-PET response was correlated with the clinical response to the biologic treatment of RA.