How selecting best upfront therapy for metastatic disease?-Focus on ROS1-rearranged disease.

ROS proto-oncogene 1 (ROS1) rearrangements defines a distinct group of non-small cell lung cancer (NSCLC), mainly represented by younger subjects, never smokers and with adenocarcinoma histology. Fusions involving ROS1 gene are present in 1-2% of lung adenocarcinomas and other solid tumors. Identification of patients harboring ROS1 rearrangements is a critical issue and current guidelines recommend screening of all advanced non-squamous NSCLC and certain squamous lung cancer patients. A number of trials have supported crizotinib as the best option for NSCLC patients with ROS1 translocations, irrespective of line of therapy. Unfortunately, the majority of patients become insensitive to crizotinib, due to the occurrence of secondary ROS1 mutations or failure within the central nervous system (CNS). Several highly potent and CNS penetrant ROS1 inhibitors have been developed and recent data highlight their potential role in the front-line treatment of this disease. Among them entrectinib, also known as RXDX-101, is a potent second-generation, multitarget oral inhibitor against the neurotrophin receptors TRKA, TRKB, TRKC ALK, and ROS1 with the ability to cross the blood-brain barrier. In the next few years, results of ongoing trials with novel ROS1 inhibitors and dedicated translational research studies might help to define the optimal sequence of treatment for ROS1-positive NSCLC patients.