Abstract 2284: Effects of smoking on breast tumor pathology

Abstract

Abstract Background Although smoking is not a well-established breast cancer risk factor, proximity of lungs to the breasts and findings that tobacco smoke constituents serve as mammary carcinogens in animal models suggests that smoking may alter the breast microenvironment and affect breast tumorigenesis. To determine how smoking influences tumor pathogenesis, the relationships between smoking and pathological characteristics and outcome were evaluated in 1,707 women with invasive breast cancer. Methods Patients enrolled in the Clinical Breast Care Project 2001-2013 filled out a questionnaire that included answers to current smoking status, current and previous pack use/day, number of years smoked, and length since last smoked. Patients were classified as never, former or current smokers. Pack years was calculated as years smoked x pack use/day. Logistic regression was performed to determine whether smoking was associated with any characteristics. Significance was defined as P<0.05 Results 55.7% of women never smoked, 31.5% were former smokers and 12.8% were current smokers. The average number or pack years was 14.5 in former smokers and 25.5 in current smokers. Current smoking status was associated with lymph node metastasis (OR 1.44; 95% CI 1.03-2.01), positive HER2 status (OR 1.54, 95% CI 1.04-2.25), larger tumor size (OR 1.55; 95% CI 1.14-2.11) and higher tumor stage (OR 1.54, 95% CI 1.16-2.04) when compared to never smokers. Former smokers were less likely to be diagnosed with later stage tumors (OR 0.77, 95% CI 0.62-0.96) compared to never smokers. No significant associations were detected when pack years were considered as a continuous variable; when categorized as 0, <20, 20-34 or >35 pack years, >35 pack years was associated with positive HER2 status (OR 1.80, 95% CI 1.06-3.03) and tumors of the ER+HER2+ subtype (OR 1.99, 95% CI 1.07-3.7). Overall survival was significantly lower for former and current smokers compared to never smokers (P=0.014); however, breast cancer specific survival did not differ significantly between groups (P=0.226). Conclusions Current smokers are at increased risk for having larger and later stage tumors with positive lymph node and HER2 status. Tumor size, stage and lymph node status are temporal factors, thus suggest that current smokers may have delayed diagnosis compared to never and former smokers. In contrast, HER2 status reflects a biological phenomenon and the risk of HER2 positivity increases with pack years, suggesting that carcinogens found in tobacco smoke may promote overexpression of HER2. Citation Format: Nicholas Costantino, Craig D. Shriver, Rachel E. Ellsworth. Effects of smoking on breast tumor pathology [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2284. doi:10.1158/1538-7445.AM2017-2284