RESUMO
UNLABELLED: Patients with Langerhans cell histiocytosis (LCH) and Erdheim-Chester disease (ECD) have a high frequency of BRAF(V600E) mutations and respond to RAF inhibitors. However, detection of mutations in tissue biopsies is particularly challenging in histiocytoses due to low tumor content and stromal contamination. We applied a droplet-digital PCR assay for quantitative detection of the BRAF(V600E) mutation in plasma and urine cell-free (cf) DNA and performed a prospective, blinded study in 30 patients with ECD/LCH. There was 100% concordance between tissue and urinary cfDNA genotype in treatment-naïve samples. cfDNA analysis facilitated identification of previously undescribed KRAS(G12S)-mutant ECD and dynamically tracked disease burden in patients treated with a variety of therapies. These results indicate that cfDNA BRAF(V600E) mutational analysis in plasma and urine provides a convenient and reliable method of detecting mutational status and can serve as a noninvasive biomarker to monitor response to therapy in LCH and ECD. SIGNIFICANCE: Patients with BRAF(V600E)-mutant histiocytic disorders have remarkable responses to RAF inhibition, but mutation detection in tissue in these disorders is challenging. Here, we identify that analysis of plasma and urinary cfDNA provides a reliable method to detect the BRAF(V600E) mutation and monitor response to therapy in these disorders.
Assuntos
Histiocitose/genética , Mutação , Proteínas Proto-Oncogênicas B-raf/genética , Adolescente , Adulto , Idoso , Substituição de Aminoácidos , Biópsia , Criança , Códon , Estudos Transversais , Análise Mutacional de DNA , Doença de Erdheim-Chester/diagnóstico , Doença de Erdheim-Chester/genética , Feminino , Frequência do Gene , Genes ras , Genótipo , Histiocitose/diagnóstico , Histiocitose/tratamento farmacológico , Histiocitose de Células de Langerhans/diagnóstico , Histiocitose de Células de Langerhans/genética , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Tomografia por Emissão de Pósitrons , Adulto JovemRESUMO
Erdheim-Chester disease (ECD) is a rare histiocytosis with a high prevalence of BRAF V600E mutation (>50% of patients). Patients with BRAF-mutant ECD can respond to BRAF inhibitors. Unfortunately, the lack of adequate archival tissue often precludes BRAF testing. We hypothesized that cell-free DNA (cfDNA) from plasma or urine can offer an alternative source of biologic material for testing. We tested for BRAF V600E mutation in cfDNA from the plasma and urine of 6 ECD patients. In patients with available archival tissue, the result of BRAF mutation analysis was concordant with plasma and urine cfDNA results in all 3 patients (100% agreement, kappa 1.00). In all 6 patients, BRAF mutation analysis of plasma and urine cfDNA was concordant in 5 of 6 patients (83% agreement, kappa 0.67). Testing for BRAF V600E mutation in plasma and urine cfDNA should be further investigated as an alternative to archival tissue mutation analysis.
