ROS-1

What is ROS-1 test?

The ROS1 gene test by IHC refers to the use of Immunohistochemistry (IHC) to detect ROS1 protein expression in tissue samples, typically to screen for ROS1 gene rearrangements in non-small cell lung cancer (NSCLC) and other cancers. Detects ROS1 protein overexpression, which can suggest an underlying ROS1 gene rearrangement.

Why consider ROS-1 test?

Clinicians should consider ROS1 gene rearrangement test as

• Identifies ROS1 fusions present in approximately 1–2% of NSCLC, enabling use of effective ROS1 TKIs and improving treatment outcomes compared with chemotherapy.
• Provides high analytical confidence; commonly used to confirm positive or equivocal ROS1 immunohistochemistry results due to IHC’s variable specificity.
• It is recommended for lung cancer patients to determine eligibility for targeted therapy.

Who should get this ROS-1 test?

ROS1 IHC testing is primarily considered for patients with lung cancer, especially non-small cell lung cancer (NSCLC), but can be relevant in other specific scenarios as well.

ROS1 IHC should be considered in:

• Lung adenocarcinoma - Especially in younger patients (often under 60), never-smokers or light smokers and those with no other driver mutations (e.g., EGFR, ALK, KRAS).
• Advanced or metastatic NSCLC when systemic targeted therapy is being considered

More Information about ROS-1 test

ROS1 is a proto-oncogene that encodes a receptor tyrosine kinase. In some cancers, especially NSCLC, ROS1 undergoes rearrangements (gene fusions) that lead to abnormal activation of the kinase, promoting tumor growth. These ROS1 fusions are targetable with specific tyrosine kinase inhibitors like crizotinib, making detection clinically important. 

Other Names – ROS1 by IHC, ROS1 IHC test, ROS1 for lung cancer, ROS1 NSCLC test