Depending on the type of cancer, certain biomarker tests are needed in order to decide on a treatment strategy (e.g., RAS/BRAF testing for colorectal cancer; an HER2 testing for gastric cancer; and EGFR, ALK, ROS1, and PD-L1 expression testing for non-small-cell lung cancer). The gene discussed is ROS1; the disease is colorectal cancer.