Geoffrey Kabat's recent "Takeaways from new research on lung cancer in smokers and never smokers"

Over at Genetic Literacy Project, Geffrey Kabat has taken a tour of recent progress in lung cancer management, with some encouraging insights being discovered (go to title link at this current for the full story):

First, epidemiologic studies investigating low-level, hard-to-measure, or subtle exposures, such as environmental tobacco smoke, radon exposure, and asbestos should focus on validated lifetime non-smokers, since smoking is such a powerful risk factor for lung cancer. (The risk of lung cancer posed by smoking is much stronger than that posed by asbestos). 

Because so little is known about the causes of [lung cancer in never smokers] LCINS, there may be a tendency to overstate the importance of associations with potential risk factors that have been studied, rather than acknowledge that the findings of these studies are unlikely to account for a large proportion of LCINS.

In regard to passive smoking, a French study that examined major mutations associated with lung cancer in never smokers and smokers found no clear association between passive smoke exposure and a “smoker-like mutation profile” in lifelong, never-smokers with lung cancer. They concluded that, “Passive smoking alone appeared to be insufficient to determine a somatic profile in lung cancer.”

Second, characterizing the common and divergent mechanisms of malignant transformation in lung cancer occurring among smokers and that in never smokers could contribute to a better understanding of the genomic changes underlying malignant transformation and progression. As one group of researchers wrote, “The mutually exclusive nature of certain mutations is a strong argument in favor of separate genetic paths to cancer for ever smokers and never smokers.”

Third, the difficulty of identifying major causal factors in LCINS reminds us, that for many cancers, in spite of fifty years of epidemiologic research, we still have not identified major causal factors (exposures) for many common cancers, which might lend themselves to prevention. This is true for colorectal cancer, breast cancer, pancreatic cancer, prostate cancer, brain cancer, leukemia, and others. 

This, in turn, underscores how difficult it is to pinpoint external causes of cancers that in most cases take decades to develop. Smoking as a cause of lung cancer and human papillomavirus as a cause of cervical cancer are exceptions to be noted and appreciated.

That said, we are seeing that identifying driver mutations that give rise to a particular cancer can lead to the development of effective targeted therapies that can greatly extend survival. These therapies represent long-sought, dramatic progress in treating serious cancers. This progress is independent of identifying the causal factor responsible for the cancer.

Geoffrey Kabat is a cancer epidemiologist and the author of Hyping Health Risks: Environmental Hazards in Daily Life and the Science of Epidemiology and Getting Risk Right: Understanding Science of Elusive Health Risks. He has a long-standing interest in lung cancer and, particularly, lung cancer occurring in never smokers, and has published on risk factors associated with that condition, including passive smoking, hormonal factors, and body weight.