New data challenges assumptions about smoking and lung cancer

Data presented at the recent 11th International Lung Cancer Congress challenges the commonly accepted notion that most lung cancer patients are current smokers or only recently quit after the onset of lung cancer-related symptoms.  A retrospective study of 626 lung cancer patients treated at a tertiary care center reported that 77% of patients had a smoking history--but only 14.7% were smoking at the time of diagnosis.  Moreover, 60% of the remaining patients with a smoking history had not smoked for a mean of 18 years--and the other 40% had stopped smoking within 10 years of diagnosis.  The research team was led by Dr. Cindy Mong from UCLA-David Geffen School of Medicine.

In addition, a relationship between the time interval of smoking cessation and tumor histologic type was identified: patients were significantly more likely to have adenocarcinoma if more than 21 years had elapsed since they last smoked, while squamous cell carcinoma was more common in current smokers.  Interestingly, the prevalence of ACa varied inversely with the number of pack-year history.

This is intriguing (albeit somewhat discouraging) data, although it is unclear how representative these results are compared to the general population or to other areas of the U.S.  There is a referral bias toward non-smokers in this study compared to information about the general U.S. population (23% non-smokers in this study versus 9% in general) as well as an overrepresentation of lower stage patients in this study.  According to 2008 data from the CDC, only 16% of patients in the U.S. were diagnosed with localized disease compared to 59% in this study.

Nevertheless, these data are striking and, if generalized to the entire population, have long-term consequences for patients and oncology care--not to mention important health care policy implications.  Too bad we burned through all that tobacco litigation money.  We will have to do a massive education effort for patients who have ever smoked that they will be at risk for cancer for years after they quit.