ROS1 translocation testing refers to a genetic test used to identify whether a person’s cancer cells have a specific genetic abnormality of the ROS1 gene. This abnormality occurs when the ROS1 gene, which is involved in cell growth and division, fuses with another gene, leading to uncontrolled cell growth and the development of cancer.

ROS1 translocations are particularly relevant in non-small cell lung cancer (NSCLC). The ROS1 gene can fuse with many other genes. The most common in lung cancer is the CD74 gene. If a patient’s cancer cells have ROS1 translocation, targeted therapies can be used to treat the cancer more effectively. These targeted therapies such as ROS1 tyrosine kinase inhibitor (TKI) or ROS1 inhibitors (e.g. crizotinib, entrectinib) inhibit the activity of the abnormal ROS1 gene, which can slow down or stop the growth of cancer cells.