Background: Lung cancer is the most frequent cancer-related cause of death for both sexes. Smoking is the cause of most cases, but estimates show that 15-20 % of cases in the western world are not associated with tobacco. Recent evidence - based on molecular and clinical studies - indicate that lung cancer in patients who have never smoked has certain characteristics that are different from those in patients who smoke. In this article we describe some of these characteristics.
Material and methods: The present paper is based on literature identified through non-systematic searches in PubMed.
Results: Lung cancer in never-smokers is estimated to be the seventh most frequent cancer type on a global basis. A number of molecular and clinical characteristics differ between lung cancer related to tobacco use and those not related to tobacco use. 62 % of lung cancers among never-smokers are adenocarcinomas and 18 % are squamous cell carcinomas, while corresponding numbers among patients who smoke are 19 % and 53 %. The K-Ras-gene is often mutated in tumours from smokers, but seldom in tumours from non-smokers; whereas the EGFR-gene is mutated in tumours from non-smokers, and not in smokers. Also, age and sex distribution, therapy response and prognosis are shown to differ between the groups.
Interpretation: Lung cancer in never-smokers should probably be regarded as a different disease-entity than smoking-induced lung cancer. This could impact prognosis as well as treatment.