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ROS1 and Lung Cancer

Testing for errors in the ROS-1 gene helps your doctor understand your lung cancer and recommend treatments that may work better for you.

ROS1 at a Glance:

  • Errors in the ROS1 gene are one type of lung cancer biomarker.  
  • Biomarker testing can help match you to targeted treatments.
  • You can ask for testing at diagnosis or if treatment stops working.

Frequently Asked Questions about Biomarker Testing

What Is ROS1-Positive Lung Cancer?

Errors in the ROS1 gene are one type of lung cancer biomarker. A patient is said to be ROS1-positive when the ROS1 gene fuses, or joins, with part of another gene. This gene change is called a ROS1 fusion, or ROS1 rearrangement, because it changes the ROS1 gene in a way that causes uncontrolled cell growth and cancer. The ROS1 gene can fuse with many different partner genes, but the most common fusion in lung cancer is the CD74 gene. The targeted therapy for ROS1-positive lung cancer is the same regardless of the specific type of ROS1 rearrangement a patient has.

Who is more likely to have a ROS1-positive lung cancer?

ROS1 gene changes occur in about 1-2% of patients with lung cancer and generally appears in adenocarcinoma non-small cell lung cancer (NSCLC). Patients who are ROS1-positive tend to be younger than the average patient with lung cancer and have little to no smoking history. 


Why ROS1 Biomarker Testing Matters

Biomarker testing is essential for ROS1‑positive lung cancer because ROS1 fusions are rare, require specific testing to detect, and directly determine whether someone can receive highly effective ROS1‑targeted therapies. 

Biomarker testing looks for specific genetic changes in the tumor to help guide treatment. Testing includes DNA-based tests to identify changes in the genes themselves, and RNA-based tests to measure how those genes behave, giving your care team a fuller picture of your tumor makeup and available treatment options.

How Is ROS1 Testing Done?

Testing is usually done at diagnosis or when treatment changes. Your doctor will need to test your tumor through a tissue or blood (liquid) biopsy. There are several different types of tests that doctors use to look for changes, or biomarkers in your cells:

  • Fluorescence in Situ Hybridization, or FISH, analysis is a common genetic test. FISH analysis looks at changes in the chromosomes through tissue under a microscope.
  • Immunohistochemistry (IHC) looks for proteins in the cell under a microscope.
  • Next-generation sequencing (NGS), also called comprehensive biomarker testing, is when tissue from a patient's tumor (gathered from a biopsy) is placed in a machine that looks for many possible biomarkers at one time.
  • Reverse transcription polymerase chain reaction (RT-PCR) is a laboratory method used to make many copies of a specific genetic sequence for analysis.

Your doctor may perform several of these tests at the same time to help confirm results. Different biomarkers rely more heavily on certain tests.

Testing for gene fusions is usually done using next‑generation sequencing (NGS) of DNA and RNA, which can identify many different fusion partners and confirm whether a fusion is present. 

Learn more about the different types of biomarker tests. 

Understanding Your ROS1 Test Results

A ROS1‑positive result means your cancer has a ROS1 fusion, a specific genetic change that can drive tumor growth and may make you eligible for highly effective ROS1‑targeted therapies. 

A ROS1‑negative result means no ROS1 fusion was found, so treatments that specifically target ROS1‑driven cancers are unlikely to help. 

An unclear result means the test couldn’t confirm whether a ROS1 fusion is present, and your care team may recommend repeat or more advanced testing, especially RNA‑based testing, to get a more accurate answer.

How ROS1 Results Influence Treatment

A ROS1-positive test result can help guide treatment decisions. Many patients with ROS1-positive lung cancer are treated with targeted therapies called ROS1 inhibitors, which are designed to target the ROS1 fusion driving cancer growth. Treatment recommendations depend on the type of ROS1 fusion, the stage of cancer, previous treatments, and your individual situation. Other treatment options may include chemotherapy, radiation therapy, or participation in a clinical trial.

Treatment Options for ROS1-Positive Lung Cancer

Learn more about ROS1 inhibitors, how treatment plans may change over time, and the options available for people living with ROS1-positive lung cancer.
Explore ROS1 treatment options

Questions to Ask Your Doctor

Work with your doctor to discuss your goals and options each time you have to review and interpret test results to make a treatment decision. The three big questions to ask are:

  • What is the goal of this treatment?
  • What are the potential side effects?
  • What other options do I have?

Research is happening at a rapid pace, and your doctor should be up to date on the recommendations for your specific type of lung cancer. If you don’t feel comfortable with the answers you are receiving, do not hesitate to seek out a second opinion.

What to Do After ROS1 Diagnosis

Someone with a ROS1-positive lung cancer diagnosis can take several empowering steps to stay ahead of their care. These are general medical information steps, not personal medical directives, and it’s important to work closely with a qualified healthcare professional for decisions about diagnosis or treatment. 

ROS1 fusions are rare, so it helps to make sure your testing included broad next‑generation sequencing (NGS), especially RNA‑based testing, which is best at identifying the specific ROS1 fusion partner. 

If you have a ROS1 fusion, you may be eligible for highly effective targeted treatments such as crizotinib, entrectinib, or repotrectinib, as well as new therapies being studied in clinical trials; your care team can explain which options fit your situation. 

Keeping notes on how you feel helps your team support you, adjust treatment if needed, and make sure your care aligns with your goals and preferences. 

Support and Patient Experiences

Whether you're newly diagnosed or navigating treatment, support resources and patient experiences can help you better understand your options and connect with others.

Connect with Support Resources

Hear From Other Patients

In this video, John shares his advice for people who have recently been diagnosed with ROS1-positive lung cancer, including the importance of support, education, and hope.

ROS1-positive lung cancer patient, John, shares what he would tell a newly diagnosed ROS1-positive lung cancer patient.

Video transcript

Lung cancer research can move at a rapid pace. Always speak with your doctor about the most up-to-date treatment guidelines.

Medically reviewed by: Jorge Gomez, MD
Last reviewed: June 2026 

Page last updated: August 13, 2026

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