Abstract 693: [18f] FDG-PET Changes after 2 Weeks of Infliximab Treatment Correlate with Long-Term Clinical Outcome in Rheumatoid Arthritis Patients
Authors
EH Elzinga, CJ van der Laken, EFI Comans, OS Hoekstra, AA. Lammertsma, BAC Dijkmans, AE Voskuyl.
Background:
Positron emission tomography (PET) using [18F]-fluoro-2-deoxyglucose (FDG) has been described as a sensitive non-invasive method to visualize disease activity in RA. The purpose of the study was to investigate whether a change in FDG uptake after 2 weeks of infliximab treatment is associated with long-term clinical outcome in patients with RA.
Methods:
17 RA patients, with a disease activity score (DAS) ≥ 4.5 despite the use of DMARDs were studied. DAS28 scores were performed at baseline and after 2, 14 and 22 weeks of infliximab treatment. Following i.v. injection of 370 MBq [18F]-FDG, dynamic PET scans of the hands and wrists were performed at baseline and 2 weeks after initiation of treatment. Tissue uptake of FDG was quantified using standard uptake values (SUVs) in regions of interest (ROIs) drawn upon synovial tissue of the 2nd to 5th metacarpophalangeal (MCP) and wrist joints. The mean SUV of all ROIs per patient was calculated. Using Spearman correlation coefficients, the change in mean SUV from 0 and 2 weeks was correlated with the absolute DAS-28 score after 14 and 22 weeks. In addition, these correlations were compared with the correlations of changes in ESR, CRP and DAS score from 0 to 2 weeks with the absolute DAS28 score after 14 and 22 weeks, using Spearman correlation coefficients and linear regression analysis.
Results:
Changes in mean SUV significantly correlated with absolute DAS28 at 14 and 22 weeks (r = 0.67; p<0.01 and r = 0.54; p<0.05, respectively). In addition, changes in ESR, CRP and DAS from 0 to 2 weeks did not correlate with the DAS-28 score at both time points (r<0.35; p>0,1 for all correlations). Linear regression analysis showed a larger influence of changes in mean SUV on the absolute DAS score after 14 and 22 weeks compared to changes in ESR, CRP and DAS (β = 0.4 vs 0.2, 0.1 and 0.2; p<0.05).
Conclusion:
The results indicate that early changes in FDG uptake during infliximab treatment correlated with longer-term clinical outcome in RA patients.
Editorial Comment:
A search for short term predictors of response is an area of active investigation and of significant importance moving forward the care of patients with RA. To date there have been no easily available baseline laboratory markers or clinical characteristics to define patients who will respond to a particular medication. Thus investigations are ongoing to see if short term changes in biomarkers (either biochemical or imaging) can serve as useful predictors of longer term clinical outcomes. In this study the investigators have looked at changes in PET scanning of the hands and wrists at 2 weeks and shown that improvements in PET imaging are highly correlated with improved clinical outcomes at 14 and 22 weeks, while traditional markers such as ESR and CRP were not. This is a small study but provides important preliminary data that will allow a larger study to be performed. The cost and feasibility of PET scanning on a larger scale are considerations. How this modality will compare with other forms of imaging such as power Doppler ultrasound will need to be studied. Moving forward it is anticipated that more studies of this sort will be seen. If short term predictors can be identified and validated, this information could be incorporated into clinical care and accelerate movement from one (likely ineffective) treatment to the next option.
