Retrospective evaluation of the demographic and clinical characteristics of patients with PET/CT imaging in daily rheumatology practice

Aim and objective: There is an increasing number of studies in the literature on the use of PET/CT in the diagnosis and treatment follow-up of rheumatological diseases. Although there is no rheumatological disease in which PET/CT is used as the gold standard, the use of PET/CT in large vessel vasculitis seems to precede invasive techniques in recent guidelines. In our study, it was aimed to evaluate the demographic, clinical and laboratory characteristics, diagnosis distribution, compatibility of PET/CT with other imaging methods and its role in treatment follow-up of patients who underwent PET/CT at the Department of Rheumatology at Dokuz Eylül University. Materials and Method: The patients' age, gender, comorbidities, rheumatological disease diagnoses, medications used, PET/CT withdrawal dates and diagnosis ages were recorded. The findings of other imaging studies were recorded to evaluate the consistency of the images. Control PET/CT images of the patients were evaluated by comparing them with previous imaging findings. Findings: A total of 280 patients with a mean age of 58±15 years, 179 (63.9%) women, who underwent PET/CT in the rheumatology clinic between 01.01.2010 and 31.12.2020 were included in our study. Before PET/CT, 202 (72.1%) patients had a diagnosis of rheumatologic disease. After PET/CT, 40 (48.2%) patients were diagnosed with new rheumatologic disease, 43 (41.8%) patients were diagnosed with non-rheumatologic disease. No rheumatological disease was detected in 33 (11.8%) patients after PET/CT evaluation. Rheumatological diseases diagnosed by PET/CT are respectively; large vessel vasculitis (n=11), IgG4-RD (n=10), sarcoidosis (n=9) and other (n=10). Malignancy was detected in 22 of those diagnosed other than rheumatologic disease. The distribution of cancers is; lung (n=8), lymphoma (n=3), breast (n=3) and other (n=8) cancers. LAP was present in 119 of 165 patients who underwent PET/CT to exclude malignancy, and 22 of 91 patients who underwent PET/CT for rheumatologic diagnosis. LAP was found in 45% of those diagnosed with rheumatological disease and 74.4% of those diagnosed with non-rheumatic diseases (p=0.002). The median SUVmax value of those diagnosed with rheumatologic disease (n=40) was 4.6 (3.3-7.2), and the median SUVmax value of those diagnosed with malignancy (n=22) was 8 (6.1-10.6) (p <0.05). While PET/CT imaging was performed in 18 patients for follow-up purposes, the treatment of 4 of them was changed after imaging. In patients with a diagnosis of temporal arteritis, the compatibility of PET/CT with MRI was 62.5%, with CT angiography 100%, and with Doppler USG 40%. In patients diagnosed with Takayasu's arteritis, the compatibility of PET/CT with MRI was 40%, with CT angiography 50%, and with Doppler USG 38%. Conclusion: PET/CT imaging was found to be an important adjunctive examination in the diagnosis and follow-up of sarcoidosis, large vessel vasculitis and IgG4-RD in patients evaluated in the rheumatology clinic. It has been observed that it is often used in the diagnosis and follow-up of CTD, RA, SpA and autoinflammatory diseases, to investigate the malignancies accompanying rheumatic diseases and to evaluate the characteristics of LAP. PET/CT findings provide significant benefits to the clinician in the early diagnosis of rheumatologic diseases, evaluation of their prevalence, and differentiation of malignant and infectious etiologies. Keywords: PET/CT, rheumatology, large vessel vasculitis, takayasu arteritis, lymphadenopathy,sarcoidosis,FUO,IUO