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Mortality risk in former smokers with breast cancer: Pack‐years vs . smoking status
Author(s) -
Saquib Nazmus,
Stefanick Marcia L.,
Natarajan Loki,
Pierce John P.
Publication year - 2013
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.28241
Subject(s) - medicine , breast cancer , hazard ratio , confidence interval , proportional hazards model , epidemiology , cancer , demography , smoking cessation , pathology , sociology
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.