Background/Purpose: F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) can be used to image synovial inflammation in patients with rheumatoid arthritis (RA). The development of molecular imaging methods would be beneficial, especially in RA patients. In the present study, we evaluated whether the FDG uptake of the affected joints and the axillary lymph nodes (AxLN) represented by the standardized uptake value (SUV) correlated with the clinical assessment of patients with RA. In addition, we evaluated if there was a correlation between the differences in the SUV and the improvement of the clinical findings in RA patients receiving anti-TNF therapies.

Methods: Forty-two patients (10 male, 32 female; average age: 55.67 (18-74) years) who underwent anti-TNF therapies (infliximab (IFX) for 17 patients, etanercept (ETN) for 14 patients and adalimumab (ADA) for 11 patients), were enrolled in this study. The average disease duration of these patients was 11.7 (0.6-49) years. Clinical disease activity was assessed by using disease activity scoring (DAS) 28, DAS28-CRP, Simplified Disease Activity Index (SDAI), Clinical Disease Activity Index (CDAI) and numbers of 28 tender and swollen joints count (TJC, SJC) and measuring erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), serum matrix metalloproteinase-3 (MMP-3) and rheumatoid factor (RF) at baseline (0M) and after 6 month (6M) of the therapies. FDG-PET/CT was performed 0M and 6M. The PET images were interpreted by two experienced nuclear physicians and increased FDG uptake in bilateral shoulder, elbow, wrist, hip, knee, and ankle joints and bilateral AxLN were recorded. Therapeutic response was evaluated by the changes in the sum of the maximal SUV (total SUVmax) of all 12 measured joints and the clinical findings.

Results: Before treatment, the total SUVmax was correlated with the DAS28 (r=0.532,p=0.001), DAS28-CRP (r=0.529,p<0.001), SDAI (r=0.491, p=0.001), CDAI (r=0.457, p=0.002), ESR (r=0.506, p=0.001), CRP (r=0.385, p=0.012), TJC (r=0.416, p=0.007) and SJC (r=0.467, p=0.002), respectively. The SUVs of AxLN were correlated with the SUV of the ipsilateral wrist joints. The ΔSUV, the difference in the total SUVmax before and after treatment, significantly correlated with the ΔDAS28 (r=0.498, p=0.001), ΔDAS28-CRP (r=0.517, p<0.001), ΔSDAI (r=0.550, r<0.001), ΔCDAI (r=0.534, p<0.001), ΔESR (r=0.485, p=0.001), ΔCRP (r=0.437, p=0.003), ΔTJC (r=0.447, p=0.003) and ΔSJC (r=0.525, p<0.001), respectively. ΔSUV of AxLN did not correlate with ΔCRP, ΔESR and ΔMMP-3, however, correlated with the Δ SUV of the same or other side of the wrist joint.

Conclusion: FDG-PET can image the extent of inflammation in patients with RA. In addition, the FDG uptake of the axillary lymph nodes might reflect the disease activity especially in the wrist joints. FDG-PET can be used to evaluate the response of RA patients to biological treatment.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/fdg-pet-evaluation-of-axillary-lymph-nodes-and-large-joints-of-patients-with-rheumatoid-arthritis-treated-with-anti-tnf-drugs/