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If you have non-small-cell lung cancer (NSCLC), your doctor can use comprehensive biomarker testing to see if it has certain mutations they can target with treatment.

The test is done during or after your diagnosis. Certain mutations can be "drivers" of your lung cancer. That means they’re the main cause of your cancer growth and cell division.

Epidermal growth factor receptor (EGFR) mutation is one biomarker doctors look for during testing. 

EGFR is a protein on the surface of your cells that delivers signals to them telling them to grow. When it’s mutated, it tells your cells to grow and divide too much, causing cancer.

Testing for EGFR helps your doctor choose a therapy that’s more likely to control your specific cancer. That’s the first step in precision medicine -- medicine that’s matched closely with your type and stage of lung cancer. 

What’s a Biomarker?

It’s any molecule doctors can measure in your tissues, blood, or other bodily fluids. If a test shows you have a biomarker, it can be a sign that something in your body isn’t working the way it should.

A biomarker can help your doctor better understand:

  • Whether you have a disease or condition
  • How aggressive your disease or condition is
  • How well you’ll respond to specific treatments

EGFR mutations show up as deletions (parts are missing), insertions (extra segments are present), or point mutations (only a few small nucleotides are affected) in your EGFR gene.

Who Should Get Biomarker Testing for EGFR?

About 10%-15% of all lung cancers in the U.S. have EGFR mutations. Although anyone with lung cancer can have an EGFR mutation, they usually happen in NSCLC adenocarcinomas. People with EGFR mutations also tend to be women and have little to no smoking history.

Your doctor may recommend testing if:

  • They suspect you have lung cancer and they’ve recommended a biopsy.
  • You’ve already been diagnosed with lung cancer.
  • Your lung cancer has come back after treatment.

It’s important for anyone with a lung cancer diagnosis – or suspected lung cancer – to ask their doctor whether biomarker testing for EGFR is a good option.

Your doctor can use the same tissue from your initial biopsy to both diagnose lung cancer and test for mutations.

If your doctor didn’t do biomarker testing on your tissue during diagnosis, there may be enough left for testing without having to do a second biopsy.

Another option is a liquid biopsy, which is a blood test. Liquid biopsies are quicker and less invasive than biopsies. But they may not be as sensitive for picking up results in earlier-stage cancers. A liquid biopsy can help your doctor:

  • See if you have a mutation that they can target with specific treatment
  • Decide if your cancer has become resistant to a targeted therapy and decide your next treatment option
  • Follow your response to a targeted therapy

How Can Testing Shape Treatment?

The EGFR mutation was the first biomarker researchers discovered they could find and target in lung cancer. The first targeted therapy for lung cancer worked by finding and attacking this mutation.

Drugs called EGFR inhibitors can block the signal from EGFR that tells your cells to grow. Some of these drugs can be used to treat EGFR-positive NSCLC.

Biomarker testing not only tells your doctor whether you have an EGFR mutation, but also what type. This helps them narrow down the type of treatment to use on your cancer.

  • Tyrosine kinase inhibitors (TKIs) can treat EGFR exon 19 deletions and exon 21 (L858R) substitution mutations. Receptor tyrosine kinases like EGFR transmit signals from the surface of the cell to pathways within the cell. Blocking them stops this signal from being delivered.
  • The bispecific antibody amivantamab-vmjw (Rybrevant) and the kinase inhibitor mobocertinib (Exkivity) can treat advanced NSCLC with EGFR exon 20 insertion mutations. 

Your doctor may prescribe TKIs if you have certain rare types of EGFR mutations.

EGFR-positive NSCLC has many different FDA-approved drug options. Often the cancer adapts over time to treatment and stops responding to it. Your doctor can usually switch you to another drug once one stops working.

Before switching, your doctor will likely ask you to do another biopsy to see if other biomarkers are present. This will help them decide which treatment may work best for you next.

Questions to Ask Your Doctor

In order to best understand the goal of your EGFR testing, ask your doctor:

  • Will or should I have biomarker testing?
  • How will I take the test?
  • Should I expect any complications from the test?
  • How long do results take?
  • What are some good resources for learning more about biomarker testing?
  • Will my insurance pay for my testing?
  • What biomarkers will you test for?

Once you have your results, go over them with your doctor. They’ll help you find out:

  • What your results mean
  • How your results may affect your treatment
  • If you should have a retest
  • If there are medications that target your type of lung cancer
  • If you’ll need these tests again and why
  • If there are clinical trials open to you based on your results
  • How you can get a copy of your biomarker testing report

Show Sources

Photo Credit: KTSDesign / SCIENCEPHOTOLIBRARY / Getty Images

SOURCES: “What to Know About Biomarker Testing for Lung Cancer: An Expert Q&A.”

American Lung Association: “EGFR and Lung Cancer.”

LUNGevity: “Biomarker Testing,” “Targeted Therapy,” “About EGFR-Positive Lung Cancer.”