What Is an EGFR Mutation? How Is EGFR Testing Performed in Lung Cancer?

In 1956, biochemist Dr. Cohen discovered epidermal growth factor (EGF) while investigating the mechanism behind cancer cell growth. He observed that tumor cells taken from mice and introduced into chick embryos released a substance promoting nerve development and growth in the embryos. His animal experiments showed that EGF is important not only for cancer cells but also for embryonic development and maintaining the body’s normal balance. Explaining EGF’s molecular structure took Dr. Cohen 20 years after its discovery, and he received the Nobel Prize in 1986.

EGFR is a protein receptor located on the cell surface.

This receptor has three parts: a cell-surface region where a signaling molecule binds, a cell-membrane region, and an intracellular region with enzymatic activity. Activation triggers intracellular signaling and subsequent changes within the cell. An abnormality, change, or mutation in the gene encoding EGFR can cause excessive receptor activity, increasing cancer cell growth and proliferation.

The EGF receptor also exists in normal cells, but in cancer cells it tends to be present in excessive amounts or in a mutated form.

Non-Small Cell Lung Cancer(NSCLC) shows EGFR overexpression in 70% of patients. However, the presence of an EGFR mutation determines treatment response. Approximately one in every 7 NSCLC patients, or 1 of that group, carries this mutation.

Mutation screening is particularly recommended for NSCLCsubtypes including

• adenocarcinoma
• large cell carcinoma
• cases that cannot be further subtyped,
• squamous cell carcinoma in people who have never smoked,
• and adenosquamous cell carcinoma, a mixed type.

In NSCLC with an EGFR mutation, response rates to these treatments are 50-60%.

EGFR mutations can now be tested both in tumor tissue and in blood using liquid biopsy!

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