Role of 18F-FDG PET/CT in patients affected by Langerhans cell histiocytosis.

Abstract

Langerhans cell histiocytosis (LCH) is a rare hematological disorder for which the utility of18F-FDG PET/CT is unclear. Our aim was to explore the metabolic features of LCH and the possible role of18F-FDG PET/CT in LCH evaluation. We found 17 patients with histologically proven LCH who underwent 1718F-FDG PET/CT scans for staging and 42 scans for restaging/follow-up purposes. PET/CT results were compared with those obtained from other conventional imaging modalities (bone scintigraphy, plain radiogram, computed tomography, magnetic resonance). 18F-FDG PET/CT was positive in 15/17 patients, and it detected 36/37 lesions; all bone and extraskeletal lesions, except for a cecal lesion, were18F-FDG-avid. Only 1/4 of the patients with lung LCH had hypermetabolic lesions. The average SUVmax of the FDG-avid lesions was 7.3±6.7, the average lesion-to-liver SUVmax ratio was 3.4±2.5, and the average lesion-to-blood pool SUVmax ratio was 4±3.2. In comparison to other imaging methods,18F-FDG PET/CT detected additional lesions or was able to evaluate treatment response earlier in 33/74 cases; it was confirmatory in 38/74 and detected fewer lesions in 3/74 (all three with lung LCH). 18F-FDG PET/CT seems to be useful for evaluating LCH when compared to conventional imaging, except in pulmonary cases. It can be used both for staging and restaging purposes.