Passive Smoking Exposure from Partners as a Risk Factor for ER+/PR+ Double Positive Breast Cancer in Never-Smoking Chinese Urban Women: A Hospital-Based Matched Case Control Study

BACKGROUND The relationship between passive smoking exposure (PSE) and breast cancer risk is of major interest. OBJECTIVE To evaluate the relationship between PSE from partners and breast cancer risk stratified by hormone-receptor (HR) status in Chinese urban women population. DESIGN Hospital-based matched case control study. SETTING Chinese urban breast cancer patients without current or previous active smoking history in China Medical University 1st Hospital, Liaoning Province, China between Jan 2009 and Nov 2009. PATIENTS Each breast cancer patient was matched 1∶1 with healthy controls by gender and age (±2 years) from the same hospital. MEASUREMENTS The authors used unconditional logistic regression analyses to estimate odds ratio for women with PSE from partners and breast cancer risk. RESULTS 312 pairs were included in the study. Women who endured PSE had significantly increased risk of breast cancer (adjusted OR: 1.46; 95% CI: 1.05-2.03; P = 0.027), comparing with unexposed women. Women who exposed to >5 cigarettes/day also had significant increased risk (adjusted OR: 1.99; 95% CI: 1.28-3.10; P = 0.002), as were women exposed to passive smoke for 16-25 years (adjusted OR: 1.87 95% CI: 1.22-2.86; P = 0.004), and those exposed to > 4 pack-years (adjusted OR: 1.71 95% CI: 1.17-2.50; P = 0.004). Similar trends were significant for estrogen receptor (ER)/progesterone receptor (PR) double positive subgroup(adjusted OR: 1.71; 2.20; 1.99; 1.92, respectively), but not for ER+/PR-, ER-/PR+, or ER-/PR- subgroups. LIMITATIONS limitations of the hospital-based retrospective study, lack of information on entire lifetime PSE and low statistical power. CONCLUSIONS Our findings provide further evidence that PSE from partners contributes to increased risk of breast cancer, especially for ER/PR double positive breast cancer, in Chinese urban women.