Background F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) can be used to image synovial inflammation in patients with rheumatoid arthritis (RA).
Objectives In the present study, we evaluated whether the FDG uptake of the affected joints represented by the 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 FDG-PET and the clinical assessments were performed prior to (0M), and 6 months (6M) after the initiation of the therapies. The clinical assessment included DAS28, DAS28-CRP, SDAI, CDAI, ESR, CRP, MMP-3, and RF. PET images were interpreted by experienced nuclear physician and increased FDG uptake in bilateral shoulder, elbow, wrist, hip, knee, and ankle joints were recorded. Therapeutic response was evaluated by the changes in the sum of the maximal SUV (SUVmax-sum) of all measured joints and the clinical findings. ΔSUV was defined as follows; ΔSUV=SUVmax-sum (0M) - SUVmax-sum (6M).
Results Forty-two patients (10 male, 32 female; average age: 55.67 (18-74) years) who underwent anti-TNF therapies (infliximab for 17, etanercept for 14 and adalimumab for 11), were assessed. The average disease duration was 11.7 (0.6-49) years. Before treatment, the average of the measured parameters were below; DAS28 5.32±1.30 (2.16-7.84), DAS28-CRP 4.50±1.24 (1.61-7.14), SDAI 26.4±14.4 (5.5-64.9), CDAI 24.1±13.5 (5.0-58.9), ESR (mm/h) 62.4±31.5 (3-115), CRP (mg/dl) 2.33±2.40 (0.03-11.30), MMP-3 (ng/ml) 285.5±274.9 (3.70-1206.1), RF (IU/ml) 249.17±938.49 (8.0-5520.0),tender joint count of 28 joints (TJC) 5.9±5.4 (0-22), swollen joint count of 28 joints (SJC) 6.9±6.3 (0-22) and SUVmax-sum 24.96±8.25 (9.92-50.69). After treatment, the average of observed value were below; DAS28 3.27±1.20 (0.77-5.74), DAS28-CRP 2.36±1.09 (0.99-4.98), SDAI 7.5±7.7 (0-30.3), CDAI 6.8±6.9 (0-23.7), ESR 37.9±26.0 (2-107), CRP0.64±1.32 (0.01-7.33), MMP-3 131.9±157.8 (7.0-884.9),RF 127.1±499.4 (8.0-3220.0), TJC 1.1±1.13 (0-6), SJC 1.7.5±2.4 (0-8) and SUVmax-sum 19.42±5.32 (11.29-31.48).
Before treatment, the SUV 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).The ΔSUV 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.
Conclusions We conducted whole-body FDG-PET/CT and used the SUVmax to determine the FDG uptake. The difference in the total SUVmax between studies before and after anti-TNF therapies might reflect the changes in the disease activity resulting from the medication, because these values were significantly correlated with the differences in the DAS28, DAS28-CRP, SDAI and CDAI.
In conclusion, the FDG uptake observed in the inflamed RA joints can reflect the disease activity. FDG-PET might play an important role in the evaluation of the biological treatment for RA.
Disclosure of Interest None Declared
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