Lung cancer in never smokers: a review

Our plain-English summary of Lung cancer in never smokers: a review, by J. Subramanian, R. Govindan (Journal of Clinical Oncology, 2007).

The study

• Authors: J. Subramanian, R. Govindan
• Journal: Journal of Clinical Oncology
• Published: 2007;25(5):561-70
• Type of article: Review
• Cited by: 527 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Lung cancer is the leading cause of cancer-related death in the United States. Although tobacco smoking accounts for the majority of lung cancer, approximately 10% of patients with lung cancer in the United States are lifelong never smokers. Lung cancer in the never smokers (LCINS) affects women disproportionately more often than men. Only limited data are available on the etiopathogenesis, molecular abnormalities, and prognosis of LCINS. Several etiologic factors have been proposed for the development of LCINS, including exposure to radon, cooking fumes, asbestos, heavy metals, and environmental tobacco smoke, human papillomavirus infection, and inherited genetic susceptibility. However, the relative significance of these individual factors among different ethnic populations in the development of LCINS has not been well-characterized. Adenocarcinoma is the predominant histologic subtype reported with LCINS. Striking differences in response rates and outcomes are seen when patients with advanced non-small-cell lung cancer (NSCLC) who are lifelong never smokers are treated with epidermal growth factor receptor tyrosine kinase (EGFR-TK) inhibitors such as gefitinib or erlotinib compared with the outcomes with these agents in patients with tobacco-associated lung cancer. Interestingly, the activating mutations in the EGFR-TK inhibitors have been reported significantly more frequently in LCINS than in patients with tobacco-related NSCLC. This review will summarize available data on the epidemiology, risk factors, molecular genetics, management options, and outcomes of LCINS.

In plain English

This article was a review, not a new study. The authors searched MEDLINE through PubMed, mostly for articles from the previous 10 years with English abstracts, and summarized what was known about lung cancer in people who never smoked, including its possible causes, molecular features, treatment and survival. They reported that about 10% of US lung cancer patients are lifelong never smokers, and that adenocarcinoma makes up nearly 60% of these cancers. Possible causes discussed included second-hand smoke, cooking fumes, radon, asbestos, heavy metals, inherited genes, hormones, earlier lung disease and human papillomavirus. On asbestos, the review cited a Dutch cohort study that reported a relative risk for lung cancer of 3.5 with occupational exposure, after controlling for age, smoking and vitamin intake. It also cited a Quebec study of women in asbestos mining areas that found no significant increase in lung cancer deaths from non-occupational exposure (standardized proportionate mortality ratio 1.1, 95% CI 0.88 to 1.38). The authors noted that this population was exposed mainly to chrysotile, which may explain the lack of association. The authors concluded that lung cancer in never smokers is a distinct disease.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: narrative literature review
• Who was studied: published articles found in MEDLINE through PubMed, mainly from the 10 years before the review, limited to articles with English abstracts, on lung cancer in never smokers
• Exposure: proposed risk factors for lung cancer in never smokers: radon, cooking fumes, asbestos, heavy metals, environmental tobacco smoke, human papillomavirus infection and inherited genetic susceptibility
• Main results:
  • About 10% of patients with lung cancer in the United States are lifelong never smokers.
  • Adenocarcinoma accounts for nearly 60% of lung cancers in never smokers, based on the studies in the review's Table 1.
  • A cited cohort study in Holland reported an increased relative risk for lung cancer of 3.5 with occupational asbestos exposure, after controlling for age, smoking and vitamin intake.
  • A cited retrospective study of women in asbestos mining areas of Quebec (1970 to 1989) did not find a significant increase in lung cancer mortality from non-occupational exposure: the standardized proportionate mortality ratio was 1.1 (95% CI, 0.88 to 1.38).
  • The authors noted that the Quebec study population was exposed mainly to chrysotile fibers, which they said may explain the lack of association.
  • The authors judged that environmental tobacco smoke plays at best a modest role in lung cancer in never smokers.
  • The authors judged that prolonged radon exposure is associated with increased lung cancer risk, based on case-control studies and data from uranium miners.
  • A cited study found that response rates to gefitinib were higher in never smokers than in patients with tobacco-related lung cancer (36% vs 8%).
• The authors' conclusion: The authors concluded that lung cancer in never smokers is a distinct disease with its own molecular and biologic characteristics. On asbestos, they stated that the cited studies indicate non-occupational asbestos exposure may not have a significant role in increasing mortality from lung cancer in never smokers.
• Limitations the authors state:
  • The authors stated that only limited data are available on the causes, molecular abnormalities and prognosis of lung cancer in never smokers.
  • The authors stated that the relative importance of the individual risk factors in different ethnic populations has not been well characterized.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Lung Cancer, Prognosis, Adenocarcinoma, Histological Subtype, EGFR, Epidemiology.

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