This news could leave you gasping: Lung cancer—which kills more people than any other cancer—can develop slowly for 20 years before it becomes aggressive enough to detect , finds new research from University College London.
Scientists studied 25 regions of seven lung tumors surgically removed from patients. They found that certain genetic mutations occur early in a tumor’s development, probably as a result of carcinogen exposure, especially in smokers and ex-smokers. Later—likely years later—a DNA-editing protein called APOBEC mutates DNA within the tumor, and that’s when the cancer really starts to progress, says study author Elza De Bruin, Ph.D.
APOBEC usually helps your immune system, but in this case, it becomes your foe. “It normally would mutate DNA from viruses,” De Bruin says. “But now something goes wrong and the APOBEC starts to target your own DNA.”
As this process takes over, it has an even bigger impact than smoking-related mutations in smokers. APOBEC can also accelerate lung tumor growth in ex-smokers and nonsmokers, De Bruin says. The researchers discovered that the process can take 20 years while studying a tumor from an ex-smoker who kicked the habit two decades before surgery. They believe the first mutations occurred when he smoked, and APOBEC did its damage later on.
Fortunately, this doesn’t mean you’re screwed if you had a nicotine fix a few years back. You’re still better off than you would be if you hadn’t quit, says De Bruin. Smokers had about four times more mutations than ex-smokers in the study. More mutations can mean larger, more aggressive tumors, she says. However, your risk may be higher than if you’d never lit up at all, so tell your doctor about the mistakes of your past so that the two of you can watch for symptoms, like a persistent cough.
Early detection is critical. Lung cancer is often diagnosed late, when it has already spread to organs, says De Bruin. At that point, the survival rate is only 4 percent, according to the American Lung Association.
As scary as this stuff sounds, this new discovery could save lives someday: “One of the very important findings of our study is that we see these tumors actually take a very long time to develop, so there is definitely room for improvement in early detection,” says De Bruin. “One way of potentially doing that is screening patients more often.”
In the future, a blood test may help speed up diagnosis and treatment. “We are investigating if we could identify the mutations of the tumor in the blood of the patients,” she says. “If so, this might be a very easy way to detect a tumor at an early stage—hopefully when it is still curable.” Some mutations that occur early in tumor development could be blocked by drugs that are already available, says De Bruin.
For now, your best chance of surviving lung cancer is to spot it sooner than later. Check out our Guide to Lung Cancer for more on the causes, symptoms, and treatments of this deadly disease.
