title: Family history of cancer and risk of lung cancer in lifetime non-smokers and long-term ex-smokers.
abstract: BACKGROUND
  Genetic factors appear to play a role in the aetiology of lung cancer.
  
  
  METHODS
  To examine the association between family history of cancer (all types) and risk of lung cancer among non-smokers, we conducted a case-control study. Cases (n = 618) were identified through the Missouri Cancer Registry for the period 1986 through 1991, and included 432 lifetime non-smokers and 186 ex-smokers who had stopped at least 15 years prior to diagnosis or had smoked for less than one pack-year. Controls (n = 1402) were selected through drivers licence and Medicare files.
  
  
  RESULTS
  The risk of lung cancer increased directly in relation to the number of family members affected with cancer. The odds ratio (OR) associated with five or more first-degree relatives with cancer was 2.7 (95% confidence interval [CI] 1.2-6.1), with a significant linear trend in risk according to the number of relatives affected (P = 0.03). Increased lung cancer risk was associated with two or more affected siblings (OR = 1.4; 95% CI: 1.0-1.9) and with two or more affected offspring (OR = 3.2: 95% CI: 1.3-8.1). Risk was slightly elevated for family history of lung cancer (OR = 1.3; 95% CI: 1.0-1.8).
  
  
  CONCLUSIONS
  Our study identified a slight increase in risk of lung cancer in relation to five or more relatives with cancer. Preventive implications of this increased risk are unclear because the attributable fraction is low in comparison to a variety of other factors.
authors.affiliation: School of Public Health, Saint Louis University, MO 63108-3342, USA.
authors.forename: R C
authors.initials: RC
authors.lastname: Brownson
authors.forename: M C
authors.initials: MC
authors.lastname: Alavanja
authors.forename: N
authors.initials: N
authors.lastname: Caporaso
authors.forename: E
authors.initials: E
authors.lastname: Berger
authors.forename: J C
authors.initials: JC
authors.lastname: Chang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D015994:Incidence; D008175:Lung Neoplasms / Q000453:epidemiology / Q000209:etiology / Q000235:genetics*; D008875:Middle Aged; D008923:Missouri / Q000453:epidemiology; D016017:Odds Ratio; D012042:Registries; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D016540:Smoking Cessation; D011795:Surveys and Questionnaires; D015996:Survival Rate; D013997:Time Factors