Listen up, nonsmokers: this is about you.
Yes, some 80–90% of lung cancer cases befall current and former smokers. Yes, smoking is by far the number one risk factor for the disease, in addition to increasing your risk of many other cancers and of atherosclerotic cardiovascular disease (ASCVD).
But as we’ve discussed before, that leaves 10-20% of lung cancer cases—about one in seven—that afflict people who have never voluntarily inhaled.
Lung cancer in never-smokers is the fifth-greatest cause of death from cancer worldwide,1 and the seventh to ninth greatest in the United States.2 The age-adjusted incidence of lung cancer among middle-aged never-smokers in the United States is 15.2 to 20.8 cases per 100,000 person-years in women and 11.2 to 13.7 in men—rates similar to those of myeloma in men, or cervical or thyroid cancers in women.3 And as smoking rates and total lung cancer cases have declined,1 the proportion of lung cancer in nonsmokers has taken up a larger and larger share of a blessedly shrinking pie.
While lung cancer—like all cancer—is a disease of aging, and the average age at diagnosis in smokers and nonsmokers is similar, younger lung cancer patients are disproportionately never-smokers.1 Women nonsmokers are at especially high risk,* particularly if they are of Asian or Hispanic descent:4 an astounding 57.4% of Asian-American women with lung cancer, and 32.6% of Hispanic-American women, never smoked.5†
There are two categories of action you can take to protect yourself from this threat: reduce your risk of developing lung cancer, and catch it early. We’ll talk about risk reduction toward the end of this article, but our focus here is on screening for lung cancer in nonsmokers.
The United States Preventive Services Task Force (USPSTF) recommends that adults aged 50 to 80 who have smoked the equivalent of a pack a day for 20 years and who currently smoke or have quit within the past 15 years undergo annual lung cancer screening with low-dose computed tomography (low-dose CT).6 The American Cancer Society (ACS) has similar recommendations.7 This recommendation is based on seven clinical trials, the largest and most important of which were the National Lung Screening Trial (NLST, with 53,454 participants)8 and the NEderlands-Leuvens Longkanker Screenings ONderzoek (NELSON trial, with 15,792 participants).9
These organizations don’t recommend that nonsmokers get screened, but that’s not because they carefully examined evidence from screening trials of nonsmokers and determined that it wouldn’t save lives. Instead, when the USPSTF team analyzed the evidence on the value of lung cancer screening, they included trials that enrolled never-smokers,10 but they only evaluated the evidence in smokers. Moreover, the USPSTF study selection criteria excluded many studies that were conducted in never-smokers in East Asian countries.
This likely reflects their mandate to improve health at the population level, which naturally leads them to focus on the highest-risk groups. But that’s quite a different level of analysis from how you should think about the benefits and risks of screening for yourself.
To help never-smokers of a wide range of ancestries who live in the West‡ make decisions about lung cancer screening, we would ideally want to have large screening trials conducted in just such people. Unfortunately, no such trials have been conducted. We do have some studies that have evaluated the effect of screening in non-smokers,11,12,13,14,15,16,17 but as we’ll see, none of these studies are quite fit for purpose, since (first) many of these studies are observational (with all the limitations that entails), and (second) nearly all of them are conducted in nonsmokers in East Asian countries and in Western women of Asian descent, in whom the risk of lung cancer is higher than it is for most people who live in the West, and in whom the environmental and possibly genetic drivers differ. But they are the best data available for nonsmokers, and there are reasonably clear lessons to be gleaned.
