Breast cancer and smoking: A comparison of 955 breast cancer patients according to their smoking status

Aim and objective: Smoking is among the risk factors of breast cancer. The aim of this study was to compare breast cancer patients’ characteristics according to their smoking status. Methods: This study is a retrospective evaluation of all breast cancer patients treated at the General Surgery Department of University of Health Sciences, Izmir Bozyaka Research and Training Hospital, between 1982 and 2018. A total of 1459 breast cancer patients’ charts were reviewed and 955 contained data on smoking and were included in this study. There patients were classified as ever versus never smokers. Pack-years data was available for 32.3% or ever smokers. Chi square, t test, Spearman’s correlation, Kaplan Meierand Cox Regression were used for analyses. Results: Among the 955 breast cancer patients, 30.5% (n=291) were ever- and 69.5% (n=664) never smokers. According to years of diagnosis, the ratio of smokers was significantly increasing with 21.6% before 2000, 21.9% in 2000-2004, 31.1% in 2005-2009, 32.1% in 2010-2014 and 41.5% in 2015-2018 (p trend < 0.001). Ever smokers were diagnosed at a younger age (49.9±11.8 vs.54.1±13.5, p< 0.001). This was not confounded by year of diagnosis, since age at diagnosis significantly increased with increasing year of diagnosis (r=0.161, p< 0.001). ER positivity was higher among ever smokers (70.5% vs.63.2%, p=0.040) and with significant changes according to pack-year groups.No difference was found in PR positivity, mean CEA, ER%, PR%, p53%, Ki67% values and number of positive sentinel or axillary lymph nodes of ever and never smokers, while the mean CA15-3 values were significantly lower among ever smokers (17.4±10.1 vs.24.5±27.8, p< 0.001). Never smokers had a higher ratio of metastasis overall (19.5% vs.13.7%, p=0.040) and among sites, of bone metastasis (12.7% vs.6.8%, p=0.039). After adjustment for age at diagnosis, there was no significant difference in mean overall survival of ever and never smokers. Conclusions: Among breast cancer patients, ever smokers are diagnosed at a younger age compared to never smokers. More detailed evaluations could provide deeper insight in smoking-induced breast cancer.