Interest of [18F]FDG PET/CT for treatment efficacy assessment in aggressive phenotype of sarcoidosis with special emphasis on sinonasal involvement

The aim of this paper was to evaluate the clinical usefulness of [18F]FDG PET/CT for treatment efficacy assessment in patients with severe multisystemic phenotype of sarcoidosis with special emphasis on sinonasal involvement.Thirteen patients with biopsy-proven sinonasal sarcoidosis (SNS) who underwent two [18F]FDG-PET/CT were selected. PET/CT results were correlated with nasal endoscopy, biology and conventional imaging techniques (CT, MRI). Four and nine patients underwent first PET/CT before beginning treatment and during CS therapy, respectively. On the other hand, ten and three patients underwent second PET/CT during CS and after treatment withdrawal, respectively. The mean duration of clinical and endoscopic follow-up after the second scintigraphic examination was 51 months.Eleven out of 13 selected patients presented with pathological nasal endoscopy at inclusion. Among them: 1) 5 showed persistent endoscopic abnormalities at follow-up evaluation. Radiological and PET/CT imaging was consistent with these results in 4 and 5 patients, respectively; 2) 2 showed a complete endoscopic, radiologic and PET/CT normalization after CS treatment; 3) 4 showed important alterations of the sinonasal structures preventing a definitive diagnosis by endoscopic and radiologic techniques. PET/CT suggested a residual inflammatory disease in two cases. No scintigraphic abnormalities were detected in the other 2 patients. Scintigraphic results were finally confirmed by a mean follow-up of 51 months. No pathologic sinonasal [18F]FDG uptake was observed in the remaining 2/13 patients who showed doubtful endoscopic and radiologic results during primary evaluation. The stability of endoscopic results without clinical and biological evolution was observed during 39 and 38 months of follow-up after the second PET/CT.[18F]FDG PET/CT seems to be a valuable non-invasive imaging technique able to evaluate the response to treatment in aggressive SNS, identifying persistent active disease even in those patients with destructive sinonasal aftereffects and/or with atypical therapeutic evolution. Finally, [18F]FDG PET/CT could be clinically useful to modulate CS treatment eventually integrating immunosuppressive drugs.