Quitting smoking improves health and lowers odds of developing lung cancer. And even among smokers with a genetic predisposition to smoking heavily and developing lung cancer at a young age, the benefits of quitting are significant.
The findings of a new study indicate that in these high-risk smokers, quitting smoking cuts lung cancer risk in half and delays the age at which the disease is diagnosed, suggesting that doctors should consider a DNA analysis from smokers to find more effective therapies to help them quit.
For the study, published in the journal eBioMedicine, researchers analyzed data from 15 studies involving more than 12,000 current and former smokers. Even people with DNA variations that elevated their cancer risk had better outcomes if they kicked the habit.
“When people with the risky gene variants quit smoking, it cuts their odds of getting lung cancer in half,” says first author Li-Shiun Chen, assistant professor of psychiatry at Washington University in St. Louis. “We also found that although some patients will go on to develop lung cancer even after quitting, stopping smoking can delay their diagnosis by an average of seven years.”
Researchers had previously found that smokers with variations in a nicotine receptor gene were likely to continue smoking longer than those without the DNA variants. Those with the risky gene profile also were likely to be diagnosed with lung cancer about four years earlier than smokers without the risky variety of the gene, called CHRNA5.
The researchers also have repeatedly found that it’s more difficult for these people to quit. But if they can manage it, quitting can significantly lower their risk of lung cancer, on par with smokers who don’t have gene variations that make it harder to quit.
“Some people believe that genes determine everything,” Chen says. “They might think there’s no use in even trying to quit, but these findings directly contradict that myth. Although a person may be genetically vulnerable to conditions such as smoking, obesity, or metabolic syndrome, the situation isn’t hopeless. Our health may be altered by certain genes, but we still can manage to make healthier choices, and if we do that, there can be big benefits.”
Lung cancer is the most common cancer in the world, making up about 13 percent of cancer cases worldwide and contributing to more than a quarter of all cancer-related deaths. About half of those diagnosed with lung cancer will die within a year of that diagnosis.
In past research, Chen and her colleagues have found that a risky genetic profile can make a smoker more likely to respond to nicotine-replacement therapy. Because those with high-risk genes are more likely to benefit from nicotine patches and other medications, doctors might want to identify smokers who have risky genetic variants. That could make it possible to match smokers to therapies that are most likely to help them kick the habit.
“Normally, those with a risky genetic profile have difficulty quitting,” says Laura Jean Bierut, professor of psychiatry. “They are successful only about one-third as often as those who don’t have a risky gene profile. Because we also know they are more likely to respond to certain therapies, such as nicotine patches or lozenges, we should be able to use precision medicine therapies that match individual smokers to the treatments most likely to help them.”
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Funding came in part from the National Institute on Drug Abuse and the National Cancer Institute of the National Institutes of Health.