Behind the growing enthusiasm for CT lung cancer screening is a nagging question – should we be screening people who have never smoked too? It’s a dilemma that’s addressed in a new paper in Radiology that offers some insight.
CT lung screening is the only major cancer screening test that’s exclusively targeted at high-risk individuals, essentially people who have smoked long enough to meet inclusion criteria.
- Other cancer screening exams – for breast, colorectal, and cervical cancer– are offered to broader segments of the population, with age typically the only qualifying factor.
But lung cancer still occurs in people who have never smoked, who account for 10-25% of lung cancer cases, the fifth most common cause of cancer mortality globally.
- For example, East Asian women, even those who have never smoked, seem to have higher lung cancer incidence rates, indicating a genetic risk factor that’s still not fully understood.
The new Radiology paper reviews the state of knowledge regarding lung cancer in people who have never smoked, and examines whether the phenomenon’s prevalence calls for a rethinking of how CT lung cancer screening is offered.
The authors explain that lung cancer in non-smokers…
- Can be caused by environmental factors like workplace exposure, air pollution, genetic susceptibility, and exposure to second-hand smoke (20-26% higher risk for spousal exposure).
- Has a different carcinogenesis mechanism than lung cancer in smokers, and tends to be more slow-growing.
- Has different characteristics than cancer in smokers, being overwhelmingly dominated by adenocarcinoma (90%).
So with this knowledge in hand, should current U.S. and European lung cancer screening guidelines be changed?
- Japan is already conducting mass lung screening regardless of smoking history, while China’s guidelines include people who have never smoked but have other risk factors like occupational exposure.
But broader screening could lead to higher rates of overdiagnosis and overtreatment, and early studies from Asia have found screening had little effect on overall mortality in non-smokers.
- That led the Radiology authors to conclude that, at present, it’s probably not advisable to begin screening people who have never smoked until more research is conducted.
The Takeaway
The new paper on CT lung cancer screening of people who have never smoked is more than just an interesting thought experiment. It surfaces an issue that’s been percolating as risk-based lung screening gains momentum, and that ultimately may require a completely different approach to lung screening from what’s been used to date.
