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Active cigarette smoking and risk of breast cancer
Author(s) -
Catsburg Chelsea,
Miller Anthony B.,
Rohan Thomas E.
Publication year - 2014
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.29266
Subject(s) - medicine , breast cancer , hazard ratio , pregnancy , proportional hazards model , obstetrics , cohort study , confidence interval , cohort , epidemiology , gynecology , cancer , biology , genetics
Although epidemiological evidence on the role of active cigarette smoking in breast cancer risk has been inconsistent, recent literature supports a modest association between smoking and breast cancer. This association is particularly observed in women who smoke for a long duration, or who smoke for a long time prior to their first pregnancy. Here, we provide updated results on cigarette smoking and breast cancer risk in the Canadian National Breast Screening Study (NBSS). The NBSS is a large cohort of 89,835 women, aged 40–59, who were followed for a mean of 22.1 years, resulting in the ascertainment of 6,549 incident cases of breast cancer. Cox proportional hazard models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the association of cigarette smoking variables with breast cancer risk. We found breast cancer to be associated with duration (40 years vs . 0: HR = 1.57; 95%CI = 1.29–1.92), intensity (40 cigarettes per day vs . 0: HR = 1.21; 95%CI = 1.04–1.40), cumulative exposure (40 pack‐years vs . 0: HR = 1.19; 95%CI = 1.06–1.13) and latency (40 years since initiation vs . 0: HR = 1.19; 95%CI = 1.10–1.53) of cigarette smoking. Number of years smoked prior to first full‐term pregnancy was associated with higher risk of breast cancer than comparative years smoked post‐pregnancy (among parous women, 5 years pre pregnancy vs . 0: HR = 1.18; 95%CI = 1.10–1.26). These results strongly support a role for cigarette smoking in breast cancer etiology and emphasize the importance of timing of this exposure.