ABSTRACT
Objective:To investigate the clinical features of patients with Langerhans cell histiocytosis (LCH), and analyze the association between BRAF V600E mutation status and clinical features. Methods:A retrospective analysis was carried out for the clinical data of 60 patients with LCH at the Department of Pediatric Oncology, Sun Yat-sen Memorial Hospital between April 2013 and December 2019.Among them, 39 patients undertook BRAF V600E mutation testing, which in paraffin-embedded tissue samples were detected by quantitative real-time PCR (qRT-PCR), and in peripheral blood and/or bone marrow were tested by high-throughput sequencing, for analyzing the correlation between BRAF V600E mutation and clinical characteristics of LCH. Results:(1)Clinical characteristics: the age of 60 LCH patients was (4.08±0.45) years, with 43 male cases and 17 female cases.Patients at young age (≤2 years) and with risk organ (RO+ ) and central nervous system (CNS) risk lesions involvement were concentrated in the multisystem involvement (MS) group ( P<0.05). (2)Therapeutic response after induction therapy: the response to induction therapy was achieved in 28 of 60 treated patients (41.7%) and 32 (53.3%) did not.After excluding stratification factors of treatment regimen, MS ( OR=6.855, 95% CI: 2.077-22.622, P=0.002) and the age≤2 years ( OR=4.944; 95% CI: 1.601-15.275; P=0.005) were risk factors in poor chemotherapy response.RO+ ( OR=8.250, 95% CI: 1.617-42.090, P=0.005) was a significant risk factor for a poor chemotherapy response in JLSG-02 treatment group.Differently, RO+ had no dramatic effect on chemotherapy response in CCHG-LCH-2019 treatment group.(3) BRAF V600E mutation: 39 patients were determined BRAF V600E status, with the positive rate of BRAF V600E mutation in paraffin-embedded tissue samples reaching 70.3%(26 cases). BRAF V600E mutation was not associated with early treatment response, age, sex, MS and RO+ ( P>0.05). However, the positive rate of BRAF V600E in children with MS and CNS risk lesions was higher than the controls, with 76.0% (19 cases) vs.57.1% (8 cases) and 74.1% (20 cases) vs.58.3% (7 cases), respectively.Totally, 3 of 8 cases were positive in bone marrow, with 2 cases of MS, and 1 case of multiple bone invasions, and 1 of 5 cases was positive in peripheral blood, with liver and spleen being involved. Conclusions:LCH patients with age≤2 years, MS and RO+ exhibited a poor response to initial treatment, required for more aggressive treatment strategy.Lesion with activating BRAF V600E mutations suggests that LCH is a clonal disorder.There may be great variability between BRAF V600E mutations and MS as well as CNS risk lesions.In the mutation dataset, part of patients had positive BRAF V600E mutations in bone marrow/peripheral blood.This might suggest a different pathogenesis in such patients, has a certain clinical sense in some aspect.