Cigarette smoking associated with lung adenocarcinoma in situ in a large case-control study (SFBALCS)

Our plain-English summary of Cigarette smoking associated with lung adenocarcinoma in situ in a large case-control study (SFBALCS), by P.M. Bracci, J. Sison, H. Hansen, et al (Journal of Thoracic Oncology, 2012).

The study

• Authors: P.M. Bracci, J. Sison, H. Hansen, K.M. Walsh, C.P. Quesenberry, D.J. Raz, M. Wrensch, J.K. Wiencke
• Journal: Journal of Thoracic Oncology
• Published: 2012;7(9):1352-60
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Introduction: Adenocarcinoma in situ (AIS), formerly bronchioloalveolar carcinoma, is an uncommon subtype of lung adenocarcinoma and accounts for approximately 3% to 4% of lung cancers. Compared with other lung cancer histologies, AIS patients are less likely to be smokers, yet associations with other lung cancer risk factors and differences by sex have not been determined.

Methods: A total of 338 AIS patients and frequency-matched controls from the parent study (cases = 6039, controls = 2073) were included in these analyses. Odds ratios and 95% confidence intervals as estimates of the relative risk were obtained from multivariable unconditional logistic regression analyses.

Results: Risk of AIS was associated with ever smoking (OR = 2.7, 95% confidence intervals: 2.1, 3.6), increased 20% to 30% for each 10-year increase in pack-years of smoking and decreased with increased years since quitting (p for trend <0.0001). There was no evidence that risk differed by sex but there was some suggestion that risk may differ by exposure to asbestos and by second-hand tobacco smoke exposure in whites.

Conclusion: There is an association between AIS and smoking, which is smaller in magnitude than the association between other subtypes of non-small-cell lung cancer and smoking. Our findings suggesting that effects may differ by exposure to asbestos and second-hand tobacco smoke should be interpreted conservatively and warrant validation and further evaluation in larger studies of AIS.

In plain English

This was a population-based case-control study from the San Francisco Bay Area Lung Cancer Study. Among 6032 lung cancer cases diagnosed in 1998 to 2003 and 2005 to 2008, the authors studied 338 people with adenocarcinoma in situ (AIS, formerly called bronchioloalveolar carcinoma). AIS is a subtype of lung adenocarcinoma. These patients were compared with 2073 controls and with patients who had other lung cancers. Ever smoking was associated with AIS (odds ratio 2.7, 95% confidence interval 2.1 to 3.6). Risk rose with pack-years of smoking and fell with years since quitting, but it stayed raised even among people who had quit 20 or more years earlier. The authors found no evidence that the smoking link differed by sex. AIS patients were less likely than other non-small-cell lung cancer patients to be heavy smokers. Asbestos exposure was assessed from jobs and was not statistically significantly associated with AIS. Among men, the smoking-related AIS risk was greatest in those without asbestos exposure. The authors concluded that AIS is associated with smoking, but less strongly than other lung cancer subtypes. They said the findings on asbestos and second-hand smoke rest on small numbers and need confirmation in larger studies.

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: Population-based case-control study, with additional case-only comparisons between AIS and other lung cancer types
• Who was studied: 338 AIS (formerly bronchioloalveolar carcinoma) cases drawn from 6032 lung cancer cases, plus 2073 controls. Participants were residents of five San Francisco Bay Area counties, with cancers diagnosed September 1998 to March 2003 (phase I) or July 2005 to March 2008 (phase II).
• Exposure: Cigarette smoking (ever/never, pack-years, years since quitting), second-hand tobacco smoke, and asbestos exposure based on job exposure (no fiber types specified). Six lung cancer-related genetic variants (SNPs) were also examined.
• Main results:
  • Ever smokers had increased odds of AIS: OR 2.7 (95% CI 2.1, 3.6), adjusted for age, sex and race.
  • AIS risk rose with pack-years of smoking in both women and men. In the highest quartile (more than 31.5 pack-years) the OR was 5.7 (95% CI 4.2, 7.9) compared with never smokers, for men and women combined.
  • AIS risk fell with years since quitting but remained elevated in those who had quit 20 or more years earlier: men OR 2.3, women OR 1.7.
  • No evidence that the pack-years association with AIS differed by sex.
  • 63% of AIS patients were women, compared with 49.9% of all lung cancer cases.
  • Asbestos exposure was not statistically significantly associated with AIS. Whites: 200 cases and 1015 controls, OR 0.71 (95% CI 0.45, 1.1), p = 0.16. Nonwhites: 86 cases and 912 controls, OR 0.75 (95% CI 0.39, 1.4), p = 0.38.
  • Among men, the smoking-related risk of AIS was greatest among ever smokers with no asbestos exposure (p for interaction 0.02; data not shown).
  • Among whites, the smoking-related risk of AIS was greatest among ever smokers with any second-hand tobacco smoke exposure (p for interaction 0.05; data not shown).
  • AIS patients were less likely than non-AIS non-small-cell lung cancer patients to be heavy smokers (more than 31.5 pack-years): men OR 0.31, women OR 0.30.
• The authors' conclusion: The authors concluded that AIS is associated with smoking, but the association is smaller than that between smoking and other non-small-cell lung cancer subtypes. They said their findings that effects may differ by asbestos and second-hand smoke exposure should be interpreted conservatively and need validation in larger studies.
• Limitations the authors state:
  • Few cases were exposed to asbestos or unexposed to second-hand smoke, and many hypotheses were tested, so those results should be interpreted conservatively.
  • Second-hand smoke exposure may have been misclassified, particularly among nonsmokers.
  • Cancer subtypes came from registry abstracts, and other adenocarcinomas may have been misclassified as AIS.
  • Mucinous and nonmucinous AIS could not be analyzed separately.
  • Sparse data among nonwhites limited analyses by specific race groups.
  • Patients with high-grade disease who died shortly after diagnosis were likely under-represented. The authors considered survival bias unlikely for AIS.
  • The genetic analyses had small sample size and low power.

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 Adenocarcinoma, Case-Control Study, Adenocarcinoma, Carcinoma, Lung Cancer, Odds Ratio, confidence interval, Relative Risk.

Related studies

• A somatic TSHR mutation in a patient with lung adenocarcinoma with bronchioloalveolar carcinoma, coronary artery disease and severe chronic obstructive pulmonary disease — J.W. Kim, S. Lee, et al. (2012)
• The role of pemetrexed in lung adenocarcinoma, mixed subtype with bronchioloalveolar carcinoma features — M. Duruisseaux, J. Cadranel, et al. (2010)
• Association of cigarette smoking and asbestos exposure with location and histology of lung cancer — B.W. Lee, J.C. Wain, et al. (1998)
• K-ras mutations in human adenocarcinoma of the lung: association with smoking and occupational exposure to asbestos — K. Husgafvel-Pursiainen, P. Hackman, et al. (1993)
• Interaction between smoking and asbestos in human lung adenocarcinoma: role of K-ras mutations — H. Vainio, K. Husgafvel-Pursiainen, et al. (1993)
• Interaction of asbestos, age, and cigarette smoking in producing radiographic evidence of diffuse pulmonary fibrosis — K.H. Kilburn, R. Lilis, et al. (1986)

Browse more research in Journal of Thoracic Oncology, or return to medical research.