The clinical impact of serum soluble CD25 levels in children with Langerhans cell histiocytosis.

Objective: Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm with inflammatory characteristics. This study aims to investigate the correlation between sCD25 levels and clinical characteristics, as well as prognosis, in pediatric LCH.

Methods: Serum sCD25 levels were measured in 370 LCH patients under 18 years old using ELISA assays. The patients were divided into two cohorts based on different treatment regimens. We further assessed the predictive value for the prognosis impact of sCD25 in a test cohort, which was validated in the independent validation cohort.

Results: The median serum sCD25 level at diagnosis was 3908 pg/ml (range: 231-44 000pg/ml). sCD25 level was significantly higher in multi-system and risk organ positive (MS RO⁺) LCH patients compared to single-system(SS) LCH patients (p < 0.001). Patients with elevated sCD25 were more likely to have involvement of risk organs, skin, lung, lymph nodes, or pituitary (all p < 0.05). sCD25 level could predict LCH progression and relapse, with an area under the ROC curve of 60.6 %. The optimal cutoff value was determined at 2921 pg/ml. Patients in the high-sCD25 group had significantly worse progression-free survival compared to those in the low-sCD25 group (p < 0.05).

Conclusion: Elevated serum sCD25 level at initial diagnosis was associated with high-risk clinical features and worse prognosis. sCD25 level can predict the progression/recurrence of LCH following first-line chemotherapy.