# How likely is lung cancer among non-smokers? **URL:** \ **Category:** Factual Questions\ **Created:** [October 22, 2011, 11:58pm UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486 "2011-10-22T23:58:21Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\ **Post date:** [October 22, 2011, 11:58pm UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/1 "2011-10-22T23:58:21Z")
The title says it all. My mom died of lung cancer at age 75, but she had smoked for 25 years before finally quitting. It’s easy to blame smoking in her case, but how likely is it that someone contracts lung cancer having never smoked a day in their life (assuming they didn’t have an occupation where lung disease is prevalent)? ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [October 23, 2011, 12:11am UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/2 "2011-10-23T00:11:46Z")
It depends on several factors. Somewhere between 10% and 30% lung cancer cases occur in non-smokers. But there are other factors. People in high pollution have some increase in rates. Exposure to radiation is another factor. There may be a genetic component. And how long you live is also a factor. It’s also difficult to determine how many smokers would have contracted the disease if they hadn’t smoked. Still if you haven’t ever smoked, statistically you are way better off. ---
**Author:** ![Implicit](https://avatars.discourse-cdn.com/v4/letter/i/6a8cbe/32.png) [@Implicit](https://boards.straightdope.com/u/Implicit)\ **Post date:** [October 23, 2011, 12:12am UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/3 "2011-10-23T00:12:49Z")
From wiki: > [@"\[Lung](#): > > ([Lung cancer - Wikipedia](http://en.wikipedia.org/wiki/Lung_cancer))"]In the United States, smoking is estimated to account for 87% of lung cancer cases (90% in men and 85% in women).[23] Among male smokers, the lifetime risk of developing lung cancer is 17.2%; among female smokers, the risk is 11.6%. This risk is significantly lower in nonsmokers: 1.3% in men and 1.4% in women.[24] ---
**Author:** ![Duckster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/duckster/32/1244_2.png) [@Duckster](https://boards.straightdope.com/u/Duckster)\ **Post date:** [October 23, 2011, 12:53am UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/4 "2011-10-23T00:53:24Z")
Dana Reeve, widow of actor Christopher Reeve, died of lung cancer at age 44. She had never used tobacco. ---
**Author:** ![TreacherousCretin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/treacherouscretin/32/476_2.png) [@TreacherousCretin](https://boards.straightdope.com/u/TreacherousCretin)\ **Post date:** [October 23, 2011, 1:51am UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/5 "2011-10-23T01:51:51Z")
Didn’t lung cancer also get 35 years old and never smoked Andy Kaufman? ---
**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\ **Post date:** [October 23, 2011, 2:52am UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/6 "2011-10-23T02:52:29Z")
As mentioned there are factors beyond smoking that influence lung cancer risk, including genetics/ethnicity, underlying lung pathologies, air pollution, radon exposure and of course secondhand smoke (from living or working with smokers). I’ve seen those figures for 10-15% of lung cancer cases occurring in those who’ve never smoked, but in my pathology practice I’d estimate the incidence is skewed even more heavily towards a smoking history. There are subtypes of lung cancer (i.e. adenocarcinoma) which while linked to smoking are not that unusual in nonsmokers. On the other hand, one of the most virulent lung carcinomas (small cell carcinoma) is so heavily associated with smoking that you’d question the diagnosis if the patient had never smoked. ---
**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\ **Post date:** [October 23, 2011, 2:57am UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/7 "2011-10-23T02:57:56Z")
> [@Jackmannii](#): > > As mentioned there are factors beyond smoking that influence lung cancer risk, including genetics/ethnicity, underlying lung pathologies, air pollution, radon exposure and of course secondhand smoke (from living or working with smokers). What are the genetic factors and can I be tested to see if I have them? ---
**Author:** ![gonzomax](https://avatars.discourse-cdn.com/v4/letter/g/e8c25b/32.png) [@gonzomax](https://boards.straightdope.com/u/gonzomax)\ **Post date:** [October 23, 2011, 5:28am UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/8 "2011-10-23T05:28:57Z")
One "genetic factor’ is parents that smoke. You can be getting a pack a day through them for your young growing life. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [October 23, 2011, 6:17am UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/9 "2011-10-23T06:17:53Z")
All the statistics in the world won’t mean shit to you if _you’re the one!_ Once that happens, the probability is 100% ---
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [October 23, 2011, 1:11pm UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/10 "2011-10-23T13:11:53Z")
I could be wrong, but I don’t think anyone has identified common genetic risk factors for lung cancer. Certainly nothing you can get a test for at this time, and nothing as dramatic as the BRCA mutations that cause a significant portion of breast cancer. A lot of the time, we know that there must be some genetic factor long before we identify it. That’s just determined from epidemiology; observing that lung cancer patients have a non-zero tendency of also having a family history of lung cancer. And in the case of more and more genetic risk factors, we’re finding that much of the time there’s a vast array of variants that affect the risk factor to differing degrees. The cases where a particular variant causes (or is a strong risk factor for) some disease are exceptionally rare. ---
**Author:** ![Washoe](https://avatars.discourse-cdn.com/v4/letter/w/ecae2f/32.png) [@Washoe](https://boards.straightdope.com/u/Washoe)\ **Post date:** [October 23, 2011, 2:23pm UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/11 "2011-10-23T14:23:53Z")
I’ve always been led to believe that radon exposure is the second-leading cause of lung cancer. If you factor out tobacco use (or passive exposure) _and radon exposure_, then the probability of contracting lung cancer drops to practically zip. Moreover, I’ve read that if you live in a high-radon area, you really should install a detector in your home and take steps to reduce interior levels when they get too high. This is achieved primarily through adequate and thorough ventilation. ---
**Author:** ![No\_umlaut\_for\_U](https://avatars.discourse-cdn.com/v4/letter/n/ea5d25/32.png) [@No\_umlaut\_for\_U](https://boards.straightdope.com/u/No_umlaut_for_U)\ **Post date:** [October 23, 2011, 3:44pm UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/12 "2011-10-23T15:44:14Z")
> [@gonzomax](#): > > One "genetic factor’ is parents that smoke. You can be getting a pack a day through them for your young growing life. This. I wonder if parental smoking is more likely to cause lung disease on the asthma/COPD/emphysema scale than cancer per se. One side of my family is heavily laden with smokers. There have been 3 lung cancer deaths and two were to non-smokers. Just some anecdata for your pleasure. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [October 23, 2011, 3:53pm UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/13 "2011-10-23T15:53:59Z")
> [@No\_umlaut\_for\_U](#): > > This. > I wonder if parental smoking is more likely to cause lung disease on the asthma/COPD/emphysema scale than cancer per se. > > One side of my family is heavily laden with smokers. There have been 3 lung cancer deaths and two were to non-smokers. > > Just some anecdata for your pleasure. Without getting into the subject of second hand smoke, I’ll just mention that other diseases related to smoking far surpass lung cancer as a reason not to smoke. Lung cancer was chosen as the poster boy for anti-smoking simply as a scare tactic. ---
**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\ **Post date:** [October 23, 2011, 4:11pm UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/14 "2011-10-23T16:11:44Z")
> [@lazybratsche](#): > > I could be wrong, but I don’t think anyone has identified common genetic risk factors for lung cancer. Associations have been found. From a 2010 Medscape article which does not allow direct link access: _“Nonsmokers account for 10% to 15% of lung cancer cases in Europe and North America, 30% to 40% of cases in Asian countries, and 53% of all cases in women. Up to one third of these patients carry a newly identified susceptibility gene that reduces the expression of GPC5, a glypican gene that is suppressed in adenocarcinomas.”_ I don’t know of any reliable testing with good predictive ability that’s currently available (though there are companies offering alleged comprehensive genetic risk testing which is probably not very useful beyond potentially scaring the crap out of those who get tested). > [@TriPolar](#): > > Without getting into the subject of second hand smoke, I’ll just mention that other diseases related to smoking far surpass lung cancer as a reason not to smoke. Lung cancer was chosen as the poster boy for anti-smoking simply as a scare tactic. Cancer (especially small cell lung cancer which is overwhelmingly a fatal disease in short order) _is_ scary, and there are other cancers linked to smoking (i.e. mouth/oral cavity/larynx/bladder) which can be just as scary. Fear of cancer in general has more of an impact than the chronic diseases which smoking promotes. You can’t get people wound up as much about coronary artery disease or slow death from emphysema as your lung capacity dwindles and you wind up dependent on an oxygen tank you must wheel around everywhere you go. That last one scares me more than lung cancer, but YMMV. ---
**Author:** ![Washoe](https://avatars.discourse-cdn.com/v4/letter/w/ecae2f/32.png) [@Washoe](https://boards.straightdope.com/u/Washoe)\ **Post date:** [October 23, 2011, 4:21pm UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/15 "2011-10-23T16:21:24Z")
> [@Jackmannii](#): > > Fear of cancer in general has more of an impact than the chronic diseases which smoking promotes. You can’t get people wound up as much about coronary artery disease or slow death from emphysema as your lung capacity dwindles and you wind up dependent on an oxygen tank you must wheel around everywhere you go. My wife’s an RT. She told me that when you see an old person out and about with an O[sup]2[/sup] tank, it’s _always_ due to a history of tobacco use. Is this true, or are there other causes? ---
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [October 23, 2011, 5:04pm UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/16 "2011-10-23T17:04:10Z")
> [@Jackmannii](#): > > Associations have been found. From a 2010 Medscape article which does not allow direct link access: > > _“Nonsmokers account for 10% to 15% of lung cancer cases in Europe and North America, 30% to 40% of cases in Asian countries, and 53% of all cases in women. Up to one third of these patients carry a newly identified susceptibility gene that reduces the expression of GPC5, a glypican gene that is suppressed in adenocarcinomas.”_ Interesting, it seems I didn’t hedge my statement quite enough :D. I’ll concede the “common” point, though from the GWAS abstracts I can find on the topic it seems that the association is not particularly strong. ([This](http://www.thelancet.com/journals/lanonc/article/PIIS1470-2045%2810%2970042-5/fulltext) seems to be the original paper that identified the association with GPC5, but [a later meta-analysis](http://www.thelancet.com/journals/lanonc/article/PIIS1470-2045%2810%2970096-6/fulltext) failed to reproduce the association). ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [October 23, 2011, 5:18pm UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/17 "2011-10-23T17:18:35Z")
> [@lazybratsche](#): > > Interesting, it seems I didn’t hedge my statement quite enough :D. I’ll concede the “common” point, though from the GWAS abstracts I can find on the topic it seems that the association is not particularly strong. ([This](http://www.thelancet.com/journals/lanonc/article/PIIS1470-2045%2810%2970042-5/fulltext) seems to be the original paper that identified the association with GPC5, but [a later meta-analysis](http://www.thelancet.com/journals/lanonc/article/PIIS1470-2045%2810%2970096-6/fulltext) failed to reproduce the association). Still, the relationships between all the factors are unclear. It’s impossible to get the proper level hedging on this minor mystery. We see one component after another, but just haven’t deduced how they form the overall mechanism yet. Lot’s of science is that way. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [October 23, 2011, 5:55pm UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/18 "2011-10-23T17:55:18Z")
Very interesting. Doing a quick search reveals an interplay between genome and environmental smoke in cancer risk among never smokers. First off, among never smokers with lung cancer [activating mutations of epidermal growth receptor](http://clincancerres.aacrjournals.org/content/15/18/5646.abstract) seem to be common. > [@](#): > > Data emerging over the past several years show that lung cancers in never smokers are much more likely to carry activating mutations of the epidermal growth factor receptor (EGFR), a key oncogenic factor and direct therapeutic target of several newer anticancer drugs. EGFR mutant lung cancers may represent a distinct class of lung cancers, enriched in the never-smoking population, and less clearly linked to direct tobacco carcinogenesis But women with envivronmental exposure to tobacco who develop lung cancer seem to specifically be often [glutathione S-transferases M1 deficient](http://jnci.oxfordjournals.org/content/91/23/2009.short). > [@](#): > > When compared with never smokers who had no ETS exposure and developed lung cancer (n = 55), never smokers with exposure to ETS who developed lung cancer (n = 51) were more likely to be deficient in GSTM1 activity (i.e., were GSTM1 null) … CONCLUSIONS: A common genetic polymorphism divides the population of never smokers into two groups of approximately equal size, one (homozygous carriers of the GSTM1 null allele) that has a statistically significant greater risk of lung cancer from ETS than the other (heterozygous or homozygous carriers of the wild-type GSTM1 allele). The exact interplay between the genetic risk and environmental hits, such as ETS, radon, virues, etc., are indeed yet to be fully fleshed out. Agreed that cancer is not the worse thing smoking does. ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [October 23, 2011, 9:12pm UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/19 "2011-10-23T21:12:45Z")
> [@Washoe](#): > > I’ve always been led to believe that radon exposure is the second-leading cause of lung cancer. If you factor out tobacco use (or passive exposure) _and radon exposure_, then the probability of contracting lung cancer drops to practically zip. Moreover, I’ve read that if you live in a high-radon area, you really should install a detector in your home and take steps to reduce interior levels when they get too high. This is achieved primarily through adequate and thorough ventilation. I agree - Radon exposure is said to be the second most common cause. I’m not sure if the term “high-radon area” applies. My understanding is that two houses can be side by side, yet there may be one with high levels of radon and the other with essentially none. It depends (or so I read) if your home is situated over a “crack” in the Earth out of which radon is escaping. That being said, and as you noted, if you’re place is well vented for radon (which is different than being “well ventilated”), you don’t have to worry. In Canada, I believe it is now the case that all new homes are constructed to allow venting of any radon that has entered. ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [October 23, 2011, 9:17pm UTC](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486/20 "2011-10-23T21:17:14Z")
> [@Washoe](#): > > My wife’s an RT. She told me that when you see an old person out and about with an O[sup]2[/sup] tank, it’s _always_ due to a history of tobacco use. Is this true, or are there other causes? Sure, there are other causes: congestive heart failure (CHF), [restrictive/interstitial lung disease](http://www.mayoclinic.com/health/interstitial-lung-disease/DS00592) (sometimes just from osteoporosis), old chronic infections (e.g. [bronchiectasis](http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001199/)), . . . ETA: CHF is very common. ETA (2nd last post): your, not you’re (!) [Next page](https://boards.straightdope.com/t/how-likely-is-lung-cancer-among-non-smokers/600486.md?page=2)