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Molecular Tumor Testing

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Scientists continue to learn more and more about the molecular changes and genetic mutations that “drive” cancer growth. Molecular tumor testing is key to understanding the changes that are present in your tumor, which can help your cancer care team decide which treatments are most likely to work for your specific cancer. If your doctors have enough tissue from your initial biopsy, this tissue can be tested. If not, you may need to undergo a second biopsy or minor surgery to obtain enough tissue for a molecular tumor test.

When your doctors suspected you had cancer, they took a small portion of your tumor (a biopsy) to have it examined. A specialized doctor, called a pathologist, looked at your tumor cells under the microscope and found out you had lung cancer. The pathologist should have been able to tell whether you have small cell lung cancer or non-small cell lung cancer (NSCLC).

If you have NSCLC, the pathologist can usually tell the subtype of your tumor based on histology. Adenocarcinoma and squamous cell carcinoma are the most common subtypes of NSCLC.

Now, more detailed testing can be done on your tumor if your doctor requests it. These tests are sometimes referred to as molecular testing, or biomarker testing, and may involve:

  • looking for changes (mutations)in the DNA of the tumor.
  • looking at levels of specific proteins present in the tumor.

These characteristics cannot generally be passed from one generation to the next.

Why should my tumor be tested?

When particular tumor characteristics are found through molecular testing, targeted therapies—special lung cancer treatments designed to “target” these characteristics—may be offered to you as an option for treatment.

It is important to know if you have a tumor with one of these characteristics so you and your doctor can make well-informed decisions about your treatment. Characteristics that can be targeted with treatments currently available include:

  • Epidermal Growth Factor Receptor (EGFR) mutation
  • Anaplastic Lymphoma Kinase (ALK)
  • ROS1 rearrangement
  • T790M mutation


Gene rearrangement EGFR, ALK and ROS1 mutations turn on processes in tumors that make cancer cells uncontrollably grow and divide. Targeted therapies work by turning off these processes.

Testing for EGFR, ALK and ROS1 mutations may be recommended if you have the adenocarcinoma sub-type of NSCLC, though other sub-types can also have these mutations.


Sometimes tumors can develop new mutations that cause targeted therapies to stop working (a process known as resistance). The most common mutation that causes resistance to EGFR-targeted drugs is called T790M. You should talk to your doctor about whether your tumor should be biopsied to test for T790M.


Immunotherapy is one of the most exciting new approaches for treating lung cancer. Immunotherapies work by boosting your body's own natural defenses to fight cancer. Your doctor may recommend testing your tumor for the amount of a protein known as PD-L1 before prescribing an immunotherapy.

Clinical trials

Even if your tumor is negative for EGFR, ALK and ROS1 mutations, your tumor can still be tested for other characteristics that may allow you to access a new targeted therapy through a clinical trial. Targeted therapies for other mutations and tumor characteristics are also being tested in clinical trials, and treatments may be available to some patients. More information

How do I get my tumor tested?

If there is enough tissue from the original biopsy of your tumor, this tissue can be tested. If not, you may need a second biopsy or minor surgery to get enough tissue to test. Some doctors may also want a second biopsy to see if you have developed the T790M mutation while taking an EGFR-targeted therapy. Results are usually sent back to your doctor between 1 and 3 weeks.

If your doctor doesn’t recommend tumor testing for you, it is okay for you to ask why not. Testing may not be appropriate in all cases, but it is best for you to know as much as you can about your disease so you and your doctors can be full partners in your care. If you have questions about the response you receive from your doctor, it is okay to ask for a second opinion from another doctor.

Where can I go to get my tumor tested?

Many major medical centers, including members of the Lung Cancer Mutation Consortium (LCMC), offer molecular testing for lung cancer patients. If your medical center does not provide this testing, consider visiting an LCMC institution. Visit to find an institution near you.

What will it cost to get my tumor tested?

Most lung cancer tumor testing is covered by insurance. If you have concerns about whether your insurance will pay for tumor testing, talk with your nurse, social worker or insurance representative.

Molecular Tumor Testing BrochureThis information is also available in our brochure, Tumor Testing for Lung Cancer.

Download (PDF) >
Order free print copies online >




Learn more about the importance of molecular tumor testing. “Don’t Guess. Test.” is a social movement aimed to expand awareness and educate patients about precision medicine and the importance of comprehensive genomic testing in lung cancer. Free to Breathe is a partner on this project, and it is our hope that through this initiative, every patient with lung cancer and their families, friends and caretakers will be motivated to take action by opening a dialogue with their doctors about genomic testing to ensure all possible treatment options are explored. 





This information is not designed to be a substitute for medical advice provided by your treatment team.
Last updated 7/2017

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