What causes non–small cell lung cancer (NSCLC) in persons who have never smoked?

Updated: Jul 15, 2021
  • Author: Winston W Tan, MD, FACP; Chief Editor: Nagla Abdel Karim, MD, PhD  more...
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Secondhand smoking

Cigarette smoke containing the carcinogenic N-nitrosamines and aromatic polycyclic hydrocarbons can be inhaled passively by nonsmokers (secondhand smoke); urinary levels of these carcinogens in nonsmokers are 1-5% of those found in active smokers. As many as 25% of the lung cancers in persons who do not smoke are believed to be caused by secondhand smoke. [18]

The US Environmental Protection Agency has recognized passive smoking as a potential carcinogen. About 3000 cases of lung cancer appear to be related to passive exposure. This awareness has led to local ordinances restricting smoking in enclosed public places, including restaurants and government buildings.

Lung cancer in never-smokers

A minority of lung cancers develop in persons who have never smoked. These lung cancers are genetically distinct from smoking-related NSCLC, and this distinction may have therapeutic implications. The observed genetic differences include a lower frequency of K-ras and a higher frequency of mutations in the EGF receptor and likely are responsible for the higher efficacy of EGF receptor inhibitors in this patient population.

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