Abstract
Tobacco smoking is inconsistently associated with breast cancer. Although some studies suggest that breast cancer risk is related to passive smoking, little is known about the association with breast cancer by tumor hormone receptor status. We aimed to explore the association between lifetime passive smoking and risk of breast cancer subtypes defined by estrogen receptor and progesterone receptor status among non-smoking Caucasian women. A hospital-based case-control study was performed in 585 cases and 1170 controls aged 28–90 years. Information on lifetime passive smoking and other factors was collected via a self-administered questionnaire. Logistic regression was used for analyses restricted to the 449 cases and 930 controls who had never smoked actively. All statistical tests were two-sided. Adjusted odds ratio of breast cancer was 1.01 (95% confidence interval (CI): 0.72–1.41) in women who experienced exposure to passive smoking at work, 1.88 (95% CI: 1.38–2.55) in women who had exposure at home, and 2.80 (95% CI: 1.84–4.25) in women who were exposed at home and at work, all compared with never exposed regularly. Increased risk was associated with longer exposure: women exposed ≤ 20 years and > 20 years had 1.27 (95% CI: 0.97–1.66) and 2.64 (95% CI: 1.87–3.74) times higher risk of breast cancer compared with never exposed (Ptrend < 0.001). The association of passive smoking with hormone receptor-positive breast cancer did not differ from that with hormone receptor-negative breast cancer (Pheterogeneity > 0.05). There was evidence of interaction between passive smoking intensity and menopausal status in both overall group (P = 0.02) and hormone receptor-positive breast cancer group (P < 0.05). In Caucasian women, lifetime exposure to passive smoking is associated with the risk of breast cancer independent of tumor hormone receptor status with the strongest association in postmenopausal women.
Highlights
Tobacco smoking is defined as an agent with limited evidence in breast cancer by the International Agency for Research on Cancer [1]
This study aimed to explore the association of passive smoking with risk of breast cancer subtypes defined by tumor hormone receptor status among Caucasian women
When stratified by menopausal status, the association was stronger among postmenopausal women than premenopausal women; significant interaction between menopausal status and intensity of exposure to passive smoking was found only for estrogen receptor-positive (ER+)progesterone receptor (PR)+ breast cancer (P = 0.02) (Table 4). In this hospital-based case-control study of breast cancer among non-smoking Caucasian women, we observed a 1.9-fold increase in breast cancer risk for women exposed to passive smoking at home, a 2.8-fold increase for those exposed at home and at work, and a 2.6-fold increase in breast cancer risk for women experienced passive smoking > 20 years
Summary
Tobacco smoking is defined as an agent with limited evidence in breast cancer by the International Agency for Research on Cancer [1]. This implication is related to the inconsistency of the results from numerous studies that investigated smoking and breast cancer association [2]. Lack of significant association in active smokers is followed by underestimation of passive smoking (mainstream smoke and sidestream smoke) as a risk factor for breast cancer. The association of passive smoking with breast cancer was found in younger, primarily premenopausal women, whereas the risk in older or postmenopausal women was inconclusive [8, 12, 16, 17]. Other studies found little evidence in risk of breast cancer [18,19,20,21]
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