Non-p.V600E BRAF Mutations Are Common Using a More Sensitive and Broad Detection Tool.

Abstract

To assess the performance of a next-generation sequencing (NGS) platform for the clinical detection of BRAF mutations. In this retrospective quality assessment of an NGS assay, we analyzed BRAF mutations within parts of exons 11 and 15 in 835 neoplastic tissues submitted to our molecular diagnostics laboratory. The NGS assays detected a BRAF mutation in 5.9% of lung adenocarcinomas, 13% of colorectal cancers, and 44% of melanomas. Mutant allele frequencies were less than 20% in 28% of 88 BRAF-mutated specimens. Two lymph node specimens with subcapsular or infiltrative metastasis showed 1% to 2% mutant alleles. There were 26 unique BRAF mutations in exons 11 and 15, including three novel mutations. Mutations were located outside codon 600 in 39% of BRAF-mutated tumors. Lung adenocarcinomas showed significantly higher non-p.V600E mutations (86%) than did colorectal cancers (23%) and melanomas (34%). The three most common BRAF mutations in lung cancers accounted for only 41% of the observed BRAF mutations (p.D594G [18%], p.V600E [14%], and p.G469A [9%]). The NGS assay demonstrated a high analytic sensitivity and a broad reportable range for clinical detection of BRAF mutations. Elucidating the spectrum of non-p. V600E BRAF mutations in different malignancies is a first step toward understanding their clinical significance.