Prognostic value of disease distribution and maximum standardized uptake value in Langerhans cell histiocytosis: correlation with event-free and overall survival

Objective To evaluate the prognostic value of disease distribution patterns and the baseline metabolic parameter, maximum standardized uptake value (SUV max ), on fluorine-18 fluorodeoxyglucose PET-computed tomography (¹⁸F-FDG PET-CT) in pediatric patients with Langerhans cell histiocytosis (LCH). Methodology This retrospective study included 63 histopathologically confirmed LCH patients aged 1–18 years who underwent ¹⁸F-FDG PET-CT between August 2013 and 2025. Demographic, clinical, and imaging data were reviewed, including system involvement; risk and critical organ involvement; treatment regimens; survival time; and outcomes. Baseline SUV max and disease distribution patterns were correlated with event-free survival (EFS) and overall survival (OS). Results Of 63 patients, 40 (63.5%) were male and 23 (36.5%) females. Single-system involvement was observed in 32 (51%) patients, while 31 (49%) had multisystem disease. Risk-organ involvement (RO+) occurred in 12 (38.7%) multisystem patients, and critical organ involvement in 10 (32.2%). Diabetes insipidus was present in nine (14%) patients. Mean SUV max was significantly higher in deceased patients than survivors (6.7 ± 1.8 vs. 4.7 ± 3.0; P = 0.01). Ten-year EFS was significantly better in single-system LCH than multisystem LCH (90.6 vs. 64.5%; P = 0.03) and worse in RO+ multisystem LCH than without risk-organ–involvement multisystem LCH (50 vs. 73.7%). Ten-year OS was higher in single-system LCH than multisystem LCH (93.8 vs. 74.2%; P = 0.04) and lower in RO+ multisystem LCH (50 vs. 89.5%; P = 0.01). Conclusion Single-system LCH demonstrates significantly better survival outcomes than multisystem LCH, particularly without risk-organ involvement. Baseline SUV max appears to be a promising prognostic imaging biomarker for predicting outcomes in pediatric LCH.