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Disparities in Life Course Tobacco Exposure and Breast Cancer Risk

Institution: University of Southern California
Investigator(s): Ugonna Ihenacho,
Award Cycle: 2019 (Cycle 29) Grant #: T29DT0375 Award: $101,150
Subject Area: Tobacco-Use Prevention and Cessation
Award Type: Dissertation Awards

Initial Award Abstract
Active smoking has been associated with an increased risk of breast cancer, however many studies have found conflicting results. Findings from the Nurse's Health Study have shown that women who had ever smoked had a higher incidence of breast cancer compared to women who never smoked. Among premenopausal women, smoking was associated with an 11% increased risk of breast cancer for each additional 20 pack-years. It is unknown if these results, based largely on White professional women, apply to other racial/ethnic groups. Black women under age 40 are more likely to be diagnosed with breast cancer and have a higher rate of breast cancer related death compared to White women of the same age group. Furthermore, disparities in tobacco exposure, including age at initiation, years smoked, and secondhand exposure have been observed by race and socioeconomic status (SES). Yet, few studies have evaluated the association between smoking and breast cancer among premenopausal Black women.

I aim to address this knowledge gap in our understanding of the role of tobacco smoking in relation to the etiology of breast cancer in young Black and White women by using data from the Young Women's Health History Study, a case-control study of breast cancer conducted in Los Angeles County and Detroit (E. Velie, PI, 1R01CA136861-01A2). A total of 1,867 Non-Hispanic White and 1,362 Black women under age 50 (1,844 women with breast cancer and 1,385 women free of breast cancer) were interviewed about breast cancer risk factors, health behaviors, and health history. Extensive questions on tobacco exposure from cigarettes include prenatal exposure, personal tobacco use and secondhand exposure in childhood and adulthood.

I propose to evaluate the association between tobacco exposure and breast cancer risk using multivariate logistic regression models controlling for known breast cancer risk factors. Differences by race and SES will be evaluated. All analyses will be conducted at the University of Southern California (USC) for my dissertation development and subsequent publications. Dr. Ann Hamilton, a cancer epidemiologist and Professor in the Department of Preventive Medicine at USC, will be my primary mentor. Additionally, experts in tobacco research, environmental toxins, statistics, and breast cancer pathology are on my dissertation committee and will be involved in my training.