Crizotinib Inhibition of ROS1-Positive Tumours in Advanced Non-Small-Cell Lung Cancer: A Canadian Perspective

The ROS1 kinase is an oncogenic driver in non-small-cell lung cancer (NSCLC). Fusion events involving the ROS1 gene are found in 1%–2% of NSCLC patients and lead to deregulation of a tyrosine kinase–mediated multi-use intracellular signalling pathway, which then promotes the growth, proliferation, and progression of tumour cells. ROS1 fusion is a distinct molecular subtype of NSCLC, found independently of other recognized driver mutations, and it is predominantly identified in younger patients (<50 years of age), women, never-smokers, and patients with adenocarcinoma histology. Targeted inhibition of the aberrant ROS1 kinase with crizotinib is associated with increased progression-free survival (PFS) and improved quality-of-life measures. As the sole approved treatment for ROS1-rearranged NSCLC, crizotinib has been demonstrated, through a variety of clinical trials and retrospective analyses, to be a safe, effective, well-tolerated, and appropriate treatment for patients having the ROS1 rearrangement. Canadian physicians endorse current guidelines which recommend that all patients with nonsquamous advanced NSCLC, regardless of clinical characteristics, be tested for ROS1 rearrangement. Future integration of multigene testing panels into the standard of care could allow for efficient and cost-effective comprehensive testing of all patients with advanced nsclc. If a ROS1 rearrangement is found, treatment with crizotinib, preferably in the first-line setting, constitutes the standard of care, with other treatment options being investigated, as appropriate, should resistance to crizotinib develop.