The Added Value of 18F-FDG PET/CT in Children With Langerhans Cell Histiocytosis Presenting as a Clinically Isolated Lesion.

Abstract

Background: The clinical utility of ¹⁸F-FDG PET/CT in children diagnosed with Langerhans cell histiocytosis (LCH) who present with a clinically isolated lesion remains unclear. This study aimed to assess the added value of ¹⁸F-FDG PET/CT in identifying occult lesions and assessing its impact on disease classification and clinical outcomes in this patient population.

Methods: This retrospective study included children who underwent surgical resection of a clinically isolated lesion, were confirmed to have LCH by histopathology, and received ¹⁸F-FDG PET/CT prior to initiation of systemic therapy. Outcomes including detection of additional lesions, disease reclassification, and progression-free survival were analyzed. Kaplan-Meier analysis with log-rank test was used to compare progression-free survival between groups.

Results: A total of 44 children were included (median age 4.29 years; 70.5% male). ¹⁸F-FDG PET/CT identified additional lesions in 24 patients (54.5%), leading to reclassification as single-system multifocal disease in 10 (22.7%) and multisystem disease in 14 (31.8%). Four patients (9.1%) had risk organ involvement. ¹⁸F-FDG PET/CT findings altered the treatment strategy in 54.5% of patients. All 5 relapsed patients belonged to the group with additional lesions (p = 0.044).

Conclusion: ¹⁸F-FDG PET/CT detected additional lesions in over half of the children diagnosed with LCH presenting as a clinically isolated lesion, resulting in disease reclassification and improved risk stratification. ¹⁸F-FDG PET/CT should be routinely performed in this clinical scenario to ensure accurate staging and appropriate treatment.