The baseline metabolism parameters of 18F­FDG PET/CT as promising prognostic biomarkers in pediatric Langerhans cell histiocytosis.

Background: Langerhans cell histiocytosis (LCH) is a rare myeloid precursor cell inflammatory neoplasia, which agonizes, maims, and even kills patients. Although clinical outcomes have steadily improved over the past decades, the progression/relapse rate of LCH remains high. The purpose of this study was to evaluate the prognostic value of the pre-treatment metabolism parameters of baseline 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F­FDG PET/CT) in children with LCH. Methods: This cross-sectional study retrospectively and consecutively included 37 children (24 males and 13 females; median age, 5.1 years; range, 2.4-7.8 years) with pre-treatment 18F-FDG PET/CT from September 2020 to September 2022 in Nuclear Medicine Department, Beijing friendship hospital, Capital Medical University, Beijing, China. These patients were then all admitted to the hospital and diagnosed with LCH by biopsy, in Hematology Center, Beijing Children's Hospital, Capital Medical University, Beijing, China. Five metabolism parameters of 18F-FDG PET/CT were analyzed, including maximum standardized uptake, tumor-to-normal liver standard uptake value ratio, tumor-to-normal bone marrow standard uptake value ratio, sum of metabolic tumor volume (sMTV), and sum of total lesion glycolysis (sTLG) of all lesions. Patients were followed up for at least 1 year or until disease progression/relapse. Univariate and multivariate analyses of progression-free survival was performed. Results: During follow-up, 11 (29.7%) patients had disease progression/relapse. Univariate analysis revealed that the risk organ involvement, the treatment response at the 5th or 11th week, pre-treatment sMTV, and sTLG were significantly associated with progression-free survival (P=0.024, 0.018, 0.006, 0.006, and 0.042, respectively). Multivariate COX analysis revealed that non-response at the 11th week, pre-treatment sMTV >32.55 g/cm3, and sTLG >98.86 g (P=0.002, 0.020, 0.026, respectively) were risk factors for progression-free survival. Conclusions: The baseline metabolism parameters of 18F-FDG PET/CT could be promising imaging biomarkers for predicting prognosis in children with LCH.