One of the emerging mysteries around lung cancer is why it occurs so often in people who don’t smoke – particularly in Asia. A new paper in JAMA Network Open investigates the phenomenon by presenting results from South Korea indicating that established screening criteria would have missed nearly two-thirds of lung cancer patients.
From its earliest days, CT lung screening has been targeted at heavy smokers who have the greatest chance of developing lung cancer.
- Risk-based criteria determine who should be screened, usually based on some metric of smoking history (such as the USPSTF’s 20-pack-year threshold).
But many countries that have had national lung screening programs in place for a while – mostly in Asia – are learning that lung cancer also occurs in people who have never smoked at all.
- Whether and how to screen these individuals has become the subject of debate.
In the current study, researchers from South Korea examined 89.9k patients who were diagnosed with lung cancer from 2013 to 2018, just before the country started its national lung screening program in 2019.
- Researchers focused on whether patients would have been eligible for screening under established criteria, such as from the USPSTF, ACS, and NCCN.
Among people diagnosed with lung cancer…
- 65% would not have been eligible for lung screening under international guidelines.
- 44% had no smoking history.
- Screening eligibility differed sharply by sex, with men eligible at far higher rates than women (57% vs. 2.3%).
- Smokers who weren’t eligible for screening had 5% lower rates of all-cause mortality and 4% lower lung cancer-specific mortality than smokers who were.
- People who had never smoked had 14% lower rates of both all-cause and lung cancer-specific mortality.
The data point out an interesting dilemma inherent in CT lung cancer screening, which from the outset was set up to be risk-based rather than population-based like mammography to avoid many of screening’s downsides, like overdiagnosis.
- But that approach is missing many people who would otherwise benefit from screening, especially as we learn more about the elevated risk among many non-smoking populations, such as East Asian women.
The Takeaway
The new study shows momentum building toward broader CT lung cancer screening criteria that go beyond smoking status. The question is how quickly such criteria are adopted, and whether they gain traction outside of Asia, where recognition of lung cancer among non-smokers is growing.
