Value of 18F-FDG PET/CT Scans in Staging and Follow-Up of Pediatric Langerhans Cell Histiocytosis: Comparison to CT and/or MRI

<b>Background/Objectives</b>: The purpose of this study is to determine the added value of 18F-FDG PET/CT scan in pediatric LCH compared to other imaging modalities (CT and MRI) at initial staging, during assessment of disease reactivation, and after treatment. <b>Methods:</b> This is a retrospective study of children diagnosed with LCH between 1 June 2007 and 8 December 2022 who met the inclusion criteria. 18F-FDG PET CT imaging was compared to CT and/or MRI when available. The interclass correlation coefficient (ICC) was used to assess the agreement between methods. <i>p</i>-Values of less than 0.05 were considered statistically significant. <b>Results:</b> A total of 39 children had undergone 18F-FDG PET/CT studies. Median (range) age at presentation was 10 years (1.3-17 y), with a female-to-male ratio of 0.7:1. Excellent concordance (ICC = 1; <i>p</i> < 0.0001) between 18F-FDG PET/CT and other imaging methods was found. Median SUVmax of the positive FDG-avid lesions at initial staging was 2.7 [range 1.3-16.7]. <b>Conclusions:</b> 18F-FDG PET/CT has been shown to be complementary to diagnostic CT and MRI, with the advantage of demonstrating additional metabolic information at initial staging, during assessment of disease reactivation, and to assess interval changes post therapy. These preliminary findings warrant further investigation.