Targeting BRAF mutations in non-small cell lung cancer

Abstract

The management of non-small cell lung cancer (NSCLC) has changed significantly with the discovery of specific drug targets. These drugs have helped transform patient care and outcomes. BRAF mutated NSCLC is now recognised as a rare form of lung cancer. Data has begun to emerge supporting the use of BRAF/MEK inhibitors that target BRAF^V600E mutations in the mitogen-activated protein kinase (MAPK) pathway. Multiple phase 2 studies have been performed assessing the effectiveness of single agent BRAF inhibition and combination BRAF/MEK inhibition in pretreated and untreated patient populations. Consistently overall response rate (ORR) and progression free survival (PFS) are improved with the addition of a MEK inhibitor. A 2-cohort phase 2 study demonstrated an ORR of 33% vs. 67% and PFS of 5.5 vs. 10.2 months in those treated with single agent dabrafenib vs. dabrafenib and trametinib respectively. A similar ORR of 63% and PFS of 10.9 months was seen in a separate phase 2 study in patients treated with Dabrafenib and Trametinib in the first line setting. Immunotherapy is beginning to show promise as an active therapy in BRAF mutated NSCLC in both V600E and non-V600E subtypes; however, this requires further study and clarification. BRAF^V600E mutated NSCLC treated with chemotherapy have been widely reported to be associated with worse outcomes when compared to those without a mutation. With efficacy of combination BRAF/MEK established and early evidence of immune checkpoint inhibitor activity careful consideration should be given when choosing the most appropriate therapy in this select patient cohort.

Keywords: BRAFV600E; Non-small cell lung cancer (NSCLC); dabrafenib; trametinib; vemurafenib.

Figure 1

MAPK pathway—left: normal pathway, right: V600E mutation and target sites for BRAF and MEK inhibitors.