Vessel Wall Inflammatory Activity as Determined by F-18 Fluorodeoxyglucose PET in Large Vessel Vasculitis Is Attenuated by Immunomodulatory Drugs.

F-18 fluorodeoxyglucose (F-18 FDG) PET/CT plays an increasing role in the diagnostic workup of large vessel vasculitis (LVV); however, information on the relationship between immunosuppressive drugs and vessel wall uptake is limited. In 94 patients with a confirmed diagnosis of LVV, the vessel wall-to-liver ratio (VLR) was assessed in eight vessel segments. Patients were grouped according to intake of immunomodulatory drugs (Group 1, prednisone; Group 2, prednisone + methotrexate; and Group 3, prednisone + others) and compared to treatment-naïve individuals. A total of 54/94 (57.4%) were treated with immunomodulatory drugs (Group 1, 29/49 (53.7%); Group 2, 9/54 (16.7%); Group 3, 11/54 (20.4%); and Group 4, 5/54 (9.3%)), whereas the remainder received no therapy (40/94 (42.6%)). The mean VLR of the arterial segments correlated significantly with the hematopoietic organs (r ≥ 0.22, p ≤ 0.05), c-reactive protein (r ≥ 0.25, p ≤ 0.05), and prednisone dosage (r ≥ -0.4, p ≤ 0.05). Relative to treatment-naïve patients, a significantly lower VLR was recorded in 5/8 (62.5%) of the investigated vessel segments in Group 1 (p ≤ 0.02), in 6/8 of the vessel segments in Group 2 (75.0%, p ≤ 0.006), and in 7/8 of the segments in Group 3 (87.5%, p ≤ 0.05). In LVV, the F-18 FDG uptake in vessel wall as a marker of inflammatory activity was attenuated by immunomodulatory drugs, which provides a foundation for future serial monitoring of treatment efficacy.