Serum Cotinine and Passive Smoking Status Associated with Non-Smoking Newly Diagnosed Women with Breast Cancer in Malaysia

Background: Evidence shows that exposure to passive smoking increases the risk of breast cancer. However, there is a lack of data on the role of serum cotinine level among passive smoker women with breast cancer. The purpose of this study was to investigate the association of serum cotinine level and passive smoking exposure with the risk of breast cancer. Method: We conducted this case-control study on ۷۸ women with newly diagnosed breast cancer and ۸۳ healthy women, aged ۲۱ to ۵۹ years. Neither cases nor controls were ever smokers in their lifetime. The serum cotinine level, as a biological marker of secondhand smoking, was assessed among women exposed to passive smoking. Results: The mean serum cotinine concentrations were higher among cases compared to controls although the difference was not statistically significant (۴.۶ ± ۳.۵ ng/mL vs. ۲.۸ ± ۲.۲ ng/mL, respectively, P = ۰.۰۵۹). However, serum cotinine significantly increased the risk of breast cancer (OR = ۱.۲۲; ۹۵% CI = ۱.۰۲, ۱.۴۸, P = ۰.۰۳۴). Exposure to passive smoking at home and exposure from a smoker husband increased the risk of breast cancer compared with those with no exposure (OR = ۲.۱۷; ۹۵% CI = ۱.۱۵, ۴.۰۸, P = ۰.۰۱۶; and OR = ۲.۶۷; ۹۵% CI = ۱.۳۵, ۵.۲۹, P = ۰.۰۰۵, respectively). Conclusion: Serum cotinine levels and passive smoking exposure appeared to be independent risk factors associated with the development of breast cancer.