Real-world assessment of the BRAF status in non-squamous cell lung carcinoma using VE1 immunohistochemistry: A single laboratory experience (LPCE, Nice, France)

Introduction International guidelines recommend BRAF mutational status assessment in treatment-naive advanced non-squamous non-small cell lung carcinoma (NSCLC) patients since the presence of a BRAFV600 mutation enables specific BRAF inhibitor treatment. For this purpose, the mutational status needs to be obtained in 10 working days. Herein, we prospectively evaluated the feasibility of systematic assessment of the BRAF status using immunohistochemistry (IHC) in a single institution (LPCE, Nice) at baseline for NSCLC diagnosed. Methods 1317 NSCLC were evaluated using BRAF IHC from 2011 to 2019. Initially the BRAF status was prospectively assessed using NGS and/or pyrosequencing in 618 consecutively diagnosed NSCLC patients from 2012 to 2016; BRAFV600E and BRAF nonV600E mutated tumors detected in this cohort were retrospectively evaluated using BRAF IHC. Secondarily, 699 biopsies of NSCLC were prospectively analyzed between 2017 and 2019 using BRAF IHC. BRAF IHC positive tumors were tested using a rapid BRAF specific PCR based assay. Results Initially, 21/618 (3%) of tumors (15 early and 6 late stage tumors) were BRAFV600E mutated according to the results of NGS and/or pyrosequencing. BRAF IHC was positive in 21/21 of these cases and negative in 51/51 (100 %) BRAF non V600E mutated cases. In the prospective BRAF IHC tested cohort of patients, 24/699 (3%) tumors (13 early and 11 late stage tumors) were positive with VE1 IHC. The BRAF PCR assay was positive in 20/24 (83 %) of these cases. Conclusion BRAFV600E IHC screening of treatment-naive NSCLC patients is a rapid, specific and very sensitive method which can lead in advanced stage positive NSCLC tumors to a BRAF inhibitor treatment. This test can be routinely integrated into mandatory predictive biomarker ‘testing of NSCLC. According to the organization of patient care and the physician’s request, this practice can be proposed as an alternative to NGS-based tissue biopsy made at baseline.