Utility of FDG-PET-CT scanning in assessing the extent of disease activity and response to treatment in sarcoidosis

BACKGROUND: Radionuclide imaging modalities have increasingly been evaluated in the assessment of organ involvement in sarcoidosis. Fluoro-deoxyglucose positron emission tomography–computed tomography (FDG–PET–CT) scanning has received increasing attention in the recent years. The aim of our study was to evaluate the utility of FDG–PET–CT in determining the extent of organ involvement and disease activity in patients of sarcoidosis and to assess its utility in the evaluation of response to therapy. The secondary objective was to compare the agreement between clinical, radiological (HRCT) and metabolic indices (FDG–PET–CT) of disease activity. MATERIALS AND METHODS: This was a prospective observational study conducted between March 2007 and December 2008 at a tertiary care referral center in north India. Twenty-five symptomatic and histopathologically proven cases of sarcoidosis underwent FDG–PET–CT scanning at baseline and a follow-up scan in 21 patients at 6-9 months post-treatment with glucocorticoids. RESULTS: FDG–PET–CT scan detected metabolic disease activity in 24 of the 25 patients with clinically active sarcoidosis. It also demonstrated many clinically inapparent sites of disease activity. Complete or partial metabolic response was seen in 17 of the 21 patients in whom a follow-up scan was available. Substantial degree of agreement was found between the metabolic response and the radiological response, whereas moderate agreement was found between clinical and metabolic responses. CONCLUSIONS: FDG–PET–CT scanning is a useful imaging modality to assess disease activity, extent of disease involvement and response to treatment in clinically active sarcoidosis. There is substantial agreement between the HRCT and metabolic parameters of disease activity. Further, large sample size studies are proposed in order to identify the subset of patients who are likely to benefit the most from this sensitive modality of imaging, especially in developing countries where the cost of the procedure is an important concern.