Clinical outcomes and prognostic risk factors of Langerhans cell histiocytosis in children: Results from the BCH-LCH 2014 protocol study

Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm mainly affecting young children. This study aimed to evaluate the outcomes of 449 pediatric patients enrolled in the BCH-LCH 2014 study. 52.6% of patients were classified with single-system (SS) LCH, 28.1% with multisystem (MS) risk organ negative (RO-) LCH, and 19.4% with MS RO+ LCH. Three hundred ninety-six patients (88.2%) were initially treated with first-line therapy based on the vindesine-prednisone combination. One hundred thirty-nine patients who lacked a response to initial treatment were shifted to second-line therapy, 72 to intensive treatment Arm S1 (a combination of cytarabine, cladribine, vindesine, and dexamethasone), and 67 to Arm S2 (without cladribine). The 5-year overall survival (OS), progression-free survival (PFS), and relapse rates were 98.2% (median: 97.6 months), 54.6% (median: 58.3 months), and 29.9%, respectively. MS RO+ patients had the worst prognosis among the three clinical subtypes. For the patients initially treated with first-line therapy, the 5-year OS, PFS, and relapse rates were 99.2%, 54.5%, and 29.3%, respectively. Patients in Arm S1 had a significantly better prognosis than patients in Arm S2 (5-year PFS: 69.2% vs. 46.5%, p = .042; relapse rate: 23.4% vs. 44.2%, p = .031). Multivariate analysis revealed that early treatment response, the involvement of RO, skin, and oral mucosa, as well as laboratory parameters, including CRP and gamma-GT, were independent risk factors for the PFS of LCH. Thus, the prognosis of LCH in children has been improved significantly with stratified chemotherapy, and progression and relapse remained the challenges, especially for RO+ patients.