Lung cancer in never-smokers: A distinct illness

Lung Cancer in never-smokers is the seventh cause of cancer death worldwide. It is estimated to have a frequency ranging from 10% in Western countries to 30% in Asian countries. Some clinical characteristics are associated to lung cancer in never-smokers. It is clearly related with gender (women), ethnicity (Asian populations), and histology (adenocarcinoma). However, the relation to age is controversial. Smoking status could be a prognostic and predictive factor in lung cancer patients, but more studies are needed to demonstrate a clear association. Risk factors in never-smokers are in no way found exclusively in this subset of ever-smoker patients. These risk factors are frequently associated and sometimes cumulative or synergic. Several epidemiological studies have identified environmental tobacco smoke, occupational exposure to carcinogens, air pollution, hormonal factors, cooking oil vapors and indoor coal burning, infectious factors, genetic factors, and socioeconomic status as risk factors in never-smokers. The interest for lung cancer in never-smokers is the linkage to molecular alterations, such as epidermal growth factor receptor mutations or anaplastic lymphoma kinase translocations, that can be treated with targeted therapies and a significant increase in overall survival may be achieved.