BRAF V600E Mediates Crizotinib Resistance and Responds to Dabrafenib and Trametinib in a ROS1-Rearranged Non-Small Cell Lung Cancer: A Case Report.

ABSTRACT

Crizotinib, a multitargeted MET/ALK/ROS1 tyrosine kinase inhibitor, has been approved for the treatment of ROS1 fusion-positive non-small cell lung cancers (NSCLCs). However, "on-target" or "off-target" resistance alterations often emerge that confer the drug resistance. Patients with ROS1-rearranged NSCLC who develop crizotinib resistance, especially those acquiring "off-target" resistance mutations, still lack effective therapeutic options for after crizotinib treatment. Herein, we reported a patient with stage IVb lung adenocarcinoma harboring ROS1 fusion, who acquired a BRAF V600E and lost the ROS1 fusion after progression on crizotinib. It was deduced that the V600E may originate from a subclone with an extremely low fraction that was independent of ROS1 fusion-positive cells. The patient was subsequently treated with dabrafenib and trametinib combination and achieved a partial response lasting for more than 6 months. Our study revealed that BRAF V600E can confer the crizotinib resistance in ROS1 fusion-positive NSCLC and presented the first case showing that the treatment with dabrafenib and trametinib can serve as an effective option for later-line treatment for this molecular-defined subgroup. KEY POINTS Patients with ROS1-rearranged non-small cell lung cancer (NSCLC) who acquire "off-target" resistance mutations to crizotinib still lack effective therapeutic options for after crizotinib treatment. This report describes the case of a patient with ROS1-rearranged NSCLC who acquired a BRAF V600E and lost the ROS1 fusion after crizotinib failure. The case was subsequently treated with dabrafenib and trametinib combination and achieved a partial response lasting for more than 6 months. This is the first article reporting that treatment with dabrafenib and trametinib may serve as an effective option for later-line treatment for patients harboring resistant BRAF V600E.