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Smoking remains the biggest known cause of lung cancer, but it does not explain every diagnosis. As many as one in five people who develop the disease have never smoked, a medical puzzle that researchers may now be closer to understanding.
A large genetic study has identified a rare inherited mutation that appears to leave some people highly vulnerable to lung cancer, regardless of whether they have ever touched a cigarette.
The mutation, known as EGFR T790M, was examined using genetic and health data from more than 3.3 million people in the 23andMe database.
Across the entire study population, people carrying the mutation had a 25-fold higher risk of developing lung cancer. Among smokers, the odds were around 10 times higher.
The most striking finding involved people who had never smoked. Those carrying the mutation were more than 60 times as likely to develop lung cancer as never-smokers without it.
The discovery does not explain every case of lung cancer among non-smokers. The mutation is rare, and other genetic and environmental factors may also play a role. However, it could help doctors identify a small group of people who face an unusually high inherited risk.
At present, lung cancer screening is based largely on a person’s smoking history. That means never-smokers are not usually considered high risk, even if the disease runs in their family.
Researchers say genetic information could eventually change that approach, allowing people with certain inherited mutations to be monitored more closely and potentially diagnosed earlier.
The mutation also appears to be unusually specific. Researchers examined its possible connection to 17 other common cancers but found no clear link, suggesting its effect may be largely confined to the lungs.
Scientists first discovered EGFR T790M in 2005 in a European family with several lung cancer cases. It was later found in other families with unusually high rates of the disease, but its rarity made it difficult to calculate the danger accurately.
By studying millions of people, researchers were finally able to measure just how strongly the mutation is associated with lung cancer.
The findings offer an important clue to a question many patients and families have long asked: How can someone who has never smoked still develop lung cancer?
For some, at least, part of the answer may have been inherited.
*Source: Reuters
