Background/Purpose:

Giant cell arteritis is the most common large vessel vasculitis. ¹⁸F-FDG-PET/CT is known to be a useful imaging technique for diagnosing giant cell arteritis. Only a few ¹⁸F-FDG-PET/CT follow up studies with limited number of patients exist. Especially long term immunosuppressive treatment was so far not analyzed. Withdraw of immunosuppressive treatment is normally guided by clinical symptoms and laboratory testing. Under treatment with tocilizumab laboratory testing is not a helpful guiding tool for clinicians. ¹⁸F-FDG-PET/CT follow up investigations might be a useful diagnostic tool to decide if an immunosuppressive treatment is sufficient.

Methods:

28 patients with an active giant cell arteritis were clinically documented and subjected to ¹⁸F-FDG-PET/CT scanning with a Siemens Biograph™ TruePoint™ PET/CT. Images were evaluated by specialists at the Departments of Nuclear Medicine and Radiology of the University Clinic of Erlangen via a visual grading system. ¹⁸F-FDG-PET/CT scans were graded as active, questionable active and inactive. The scans were graded active when a vascular uptake of the tracer was higher than liver uptake. Additionally we documented the vascular uptake of the tracer applying the PETVAS score by Grayson et. (0-27). All patients received a follow up investigation to evaluate disease activity under immunosuppressive Treatment.

Results:

At time of clinically active disease in 22 patients ¹⁸F-FDG-PET/CT scans were graded as active and in 6 patients it was graded as questionable active. The mean CRP level was 52 mg/l and the mean PETVAS score was 17.86. The mean time between the first and second scan was 25.61 months. At the time of follow up only in two patients ¹⁸F-FDG-PET/CT scans were graded as active, in 13 patients as questionable active and no activity was seen in 13 patients. The mean CRP level at follow up was 9,7 mg/l and the mean PETVAS score was 8.79. Additionally to glucocorticosteroids 19 patients were treated with MTX (67,9%), 8 patients received Tocilizumab and 1 patient received Azathioprin. We couldn’t estimate any statistically significant predictors for a follow up PET-CT with no activity (= PETVAS<10) due to the small patient number. Interestingly all 8 patients (100%) with Tocilizumab treatment between the two scans were graded as no activity at follow up and had a PETVAS score <10. While 31,5% (6 patients) treated with MTX still were questionable or active in their ¹⁸F-FDG-PET/CT scan (PETVAS>10).

Conclusion:

In this follow up study we could show that ¹⁸F-FDG-PET/CT scan is a useful tool to estimate clinical remission additionally to clinical parameters and laboratory tests. Interestingly, all patients that received Tocilizumab had visually graded no activity in their ¹⁸F-FDG-PET/CT scans (PETVAS<10), while only 68.5% of the patients treated with MTX could achieve a PETVAS<10 at follow up. Larger studies on follow up ¹⁸F-FDG-PET/CT especially under Tocilizumab treatment should be done to confirm this result and the stronger immunosuppressive effect of Tocilizumab in comparison to MTX in patients with giant cell arteritis.

« Back to 2018 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/active-disease-and-follow-up-18f-fdg-pet-ct-in-patients-with-giant-cell-arteritis-which-treatment-is-more-likely-to-achieve-remission/