Understanding EGFR-Positive Lung Cancer: What Patients Need to Know

By: David Grew MD MPH

"Understanding EGFR matters because it doesn’t just explain why the cancer is growing, it helps determine how it can be treated."

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As a radiation oncologist, I often meet patients who feel overwhelmed after hearing the words “you have lung cancer”, and one of the most common questions I’m asked is why two patients with what appears to be the same lung cancer can receive very different treatments.

In many cases, the answer lies not in what the cancer looks like, but in the genetic changes driving it. This is where EGFR-positive lung cancer becomes especially important—not only for individual patients, but for the future of lung cancer research and care.

This first video in our EGFR-positive lung cancer series focuses on helping patients and families understand what EGFR means and why it matters from the very beginning.

How Lung Cancer Forms and Why EGFR Matters

Lung cancer develops when cells in the lung begin to grow in an uncontrolled way. The most common type, non-small cell lung cancer, includes adenocarcinoma, which many patients are diagnosed with today. While these cancers may look similar under a microscope, they can behave very differently depending on the molecular signals driving their growth inside the cells.

One of the most important of these signals involves a protein called EGFR, or epidermal growth factor receptor. In healthy cells, EGFR sits on the cell surface and helps regulate normal growth and repair by turning cell division on and off at the right times. In certain lung cancers, mutations in the EGFR gene disrupt this balance, causing the growth signal to remain constantly active. As a result, cancer cells continue to grow and divide even when the body is trying to stop them.

Understanding EGFR matters because it doesn’t just explain why the cancer is growing, it helps determine how it can be treated. Tumors driven by EGFR mutations often rely heavily on this single pathway to survive, making them particularly sensitive to therapies designed to block EGFR signaling. This is why identifying EGFR-positive lung cancer is such a critical step: it allows doctors to move beyond a one-size-fits-all approach and tailor treatment to the specific biology of the disease.

Understanding EGFR Mutations and Testing

Not all EGFR mutations are the same, and these differences have real implications for treatment. The most common mutations, exon 19 deletions and the L858R mutation in exon 21, lead to an overactive EGFR protein that continuously signals cancer cells to grow. These mutations are well studied and are known to respond to specific targeted therapies. Other mutations, such as exon 20 insertions and many rarer variants, can behave differently and may not respond to the same treatments. This wide range of EGFR alterations is a key reason why a personalized approach to lung cancer care is so important.

Identifying the exact EGFR mutation requires molecular testing. This is usually done by analyzing tumor tissue obtained during a biopsy, which provides the most reliable information. In some situations, a blood test called a liquid biopsy can be used to look for fragments of tumor DNA circulating in the bloodstream. While liquid biopsies can be convenient and less invasive, they do not always detect enough tumor DNA to give a clear result, making tissue testing necessary for many patients.

Although waiting for molecular test results can be stressful, this step is critical. Knowing whether a lung cancer is EGFR positive, and which specific mutation is present, allows doctors and patients to choose treatments that are better aligned with the biology of the disease. This understanding sets the foundation for more effective, individualized care and marks the start of a more informed treatment journey.

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In future blogs and videos in this series, we’ll explore how EGFR-positive lung cancer is treated at different stages and discuss what it means to live with this diagnosis.

To learn more about EGFR-positive Lung Cancer, watch the video we made here.

To learn more, browse our library of lung cancer related topics.

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