A rare genetic mutation known as EGFR T790M increases an individual’s risk of developing lung cancer by 25 times compared to those without the variant, according to a study published in the journal Science. For people who have never smoked, carriers of this specific gene variant face roughly 62 times the odds of developing lung cancer than non-carriers who also do not smoke.
The study, led by investigators at the Dana-Farber Cancer Institute and the 23andMe Research Institute, analyzed health and genetic data from more than 3.3 million people. Researchers found that while the mutation drastically escalates lung cancer risk, it showed no increased risk across 17 other types of cancers included in the analysis.
Tracing the Genetic Lineage in Southern Appalachia
Nationwide, the EGFR T790M mutation remains rare, appearing in roughly one in 15,000 to 16,000 people. However, the variant is more concentrated in specific geographic regions. In parts of Southern Appalachia, researchers estimate that as many as one in 2,000 people carry the gene variant.
Investigators traced the vast majority of U.S. carriers to a shared ancestral lineage linked to British and Irish settlers who arrived in Southern Appalachia approximately 200 to 225 years ago. According to study co-author Jaclyn LoPiccolo, an attending physician and lung cancer researcher at Dana-Farber, the mutation became enriched in the population following a founder event and genetic bottleneck in the region.
Alexander Gusev, a quantitative geneticist at Dana-Farber, described the variant’s potency as remarkable. To his knowledge, it stands as one of the strongest, if not the strongest, cancer risk-increasing mutations ever found.
Implications for Future Lung Cancer Screening
Current lung cancer screening is driven almost entirely by smoking history. However, researchers suggest these new findings could eventually shift clinical practice to incorporate inherited genetic risk into early detection protocols.
If subsequent studies confirm the benefit, individuals carrying the EGFR T790M mutation could be identified through targeted genetic testing. These carriers could then be offered personalized computed tomography (CT) screenings designed to detect lung cancers at their most curable stages.
Researchers recommend that individuals with a strong family history of lung cancer, multiple lung nodules or tumors, or family roots tracing back to the southeastern United States consider consulting a genetic counselor. A professional can help determine whether genetic testing or specialized lung cancer screening is appropriate.
Study Limitations and Expert Recommendations
Despite the strong association established between the mutation and lung cancer risk, the study authors noted several important limitations. Because the variant is rare, researchers identified relatively few carriers even among millions of participants, leaving the exact magnitude of the increased risk subject to some uncertainty.
The analysis also relied heavily on research participants from 23andMe, a population that may not fully reflect the demographic diversity of the broader public. Because the mutation is concentrated in specific U.S. regions, the exact risk estimates may not apply universally.
Researchers also emphasized that while the study demonstrates a clear genetic link, it does not prove that widespread genetic testing ultimately improves patient mortality or other health outcomes.
Addressing the interaction between genetics and lifestyle, Gusev noted that smoking and the mutation operate independently to compound danger. Smoking is harmful for lung cancer, and the mutation is harmful; when an individual experiences both, the total risk is the sum of those two factors.
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