Abstract P4-10-03: Tobacco exposure and breast cancer

Background: Smoking is a known risk factor for various types of cancer, and breast cancer patients who smoke are known to have higher breast cancer mortality. However, few studies have found an association between smoking and breast cancer incidence or tumor biology. The Athena Breast Health Network distributes an intake questionnaire at the UCSF and UCSD breast care centers which can be used to investigate links between tobacco exposure and the characteristics of incident breast cancer. Methods: Intake questionnaires were distributed to all new patients at the UCSF and UCSD breast care centers from December 2012 to May 2018. Patients who completed the questionnaire with a known diagnosis of breast cancer were compared to those without in a case-control study. Breast cancer diagnoses were determined by ICD9 diagnosis codes from the patients' medical records. The association of smoking and breast cancer prevalence and biology was analyzed using generalized linear models and Fisher tests in R. Results: Of the 7727 patients who completed the Athena intake questionnaire at UCSF and UCSD, 5499 consented to have their data used for research. A first analysis was conducted on 4175 UCSF patients alone: 2186 of the UCSF patients who had completed the questionnaire had a documented breast cancer diagnosis, vs 1989 with no known diagnosis at the time of this analysis. 1096 of the 4175 UCSF patients reported having ever smoked, including 73 who had accrued 30 or more pack years. Complete pathology data was available for 1120 cancer patients. Controlling for age, more patients with invasive breast cancer reported having ever smoked, with an odd's ratio (OR) of 2.32 (p = .0043). By including DCIS, the OR drops slightly to 2.26 (p = .0058). Taking alcohol consumption into account as a confounder lowered the OR to 2.19 (p = .0454). Overall, the risk of breast cancer increases with each additional pack year (OR = 1.08, p = .0211), independent of age. There are no significant differences in tumor biology for any smoking group. Conclusions: A history of smoking is associated with an increased risk of developing breast cancer and is directly related to cumulative pack years exposure. This association should be further validated in cohort studies. Citation Format: Dreher N, Layton TM, Parker BA, Shibley WP, Acerbi I, Wallace AM, Blair S, Pierce JP, Glantz S, Guydish J, Hiatt R, van 't Veer L, Esserman L, Athena Breast Health Network Investigators and Advocate Partners. Tobacco exposure and breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-10-03.