title: Mortality risk in former smokers with breast cancer: pack-years vs. smoking status.
abstract: It is unclear why successful quitting at time of breast cancer diagnosis should remove risk from a significant lifetime of smoking. Studies concluding this may be biased by how smoking is measured in many epidemiological cohorts. In the late 1990s, a randomized trial of diet and breast cancer outcomes enrolled early-stage female breast cancer survivors diagnosed within the previous 4 years. Smoking history and key covariate measures were available at study entry for 2,953 participants. Participants were followed for an average of 7.3 years (96% response rate). There were 10.1% deaths (83% from breast cancer). At enrollment, 55.2% were never smokers, 41.2% former smokers and 4.6% current smokers. Using current smoking status in a Cox regression, there was no increased risk for former smokers for either all-cause mortality [hazard ratio (HR) = 1.11; 95% confidence interval (CI) = 0.87-1.41; p-value = 0.42) or breast cancer mortality. However, when we categorized on extensive lifetime exposure, former smokers with 20+ pack-years of smoking (25.8%) had a significantly higher risk of both all-cause (HR = 1.77; 95% CI = 1.17-2.48; p-value = 0.0007) and breast cancer-specific mortality (HR = 1.62; 95% CI = 1.11-2.37; p-value = 0.01). Lifetime smoking exposure, not current status, should be used to assess mortality risk among former smokers.
authors: Stanford Prevention Research Center, Stanford University, Stanford, CA.
authors: Nazmus
authors: N
authors: Saquib
authors: Marcia L
authors: ML
authors: Stefanick
authors: Loki
authors: L
authors: Natarajan
authors: John P
authors: JP
authors: Pierce
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000209:etiology / Q000401:mortality*; D002140:California / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008875:Middle Aged; D016016:Proportional Hazards Models; D012306:Risk; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects / Q000401:mortality*; D055815:Young Adult
keywords: breast cancer; mortality; pack-years; smoking status
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