Abstract LB-190: Ethnic differences in the relationship between diabetes, adiposity measures and breast cancer-specific mortality
Authors: Connor Avonne E. , Visvanathan Kala , Baumgartner Kathy , Baumgartner Richard N. , Boone Stephanie , Hines Lisa M. , Giuliano Anna R. , John Esther M. , Wolff Roger K. , Slattery Martha L. 
Published: August 2015

Background: Type 2 diabetes and obesity are modifiable factors that are associated with breast cancer (BC) specific and all-cause (AC) mortality among women with BC. Few studies have examined the role of adiposity in the association between diabetes and BC outcomes, particularly among Hispanic women who have high prevalence of obesity and diabetes. We hypothesized that adiposity mediates the association between diabetes and risk of BC-specific and AC mortality in BC survivors from the Breast Cancer Health Disparities Study.

Methods: The study population included 2,478 women (1,180 Hispanics, 1,298 non-Hispanic whites (NHW)) from the San Francisco Bay Area, New Mexico, Utah, Colorado and Arizona with incident, invasive breast cancer diagnosed between April 1995 and April 2002 or between October 1999 and May 2004, depending on study site. Information on diabetes and lifestyle factors was collected by in-person interview, as well as self-reported weight and height during the referent year, and measured waist and hip circumferences. Hazard ratios (HR) and 95% confidence intervals (CI) were calculated by Cox proportional hazards regression models for overall associations and by ethnicity. Covariates of interests included ethnicity, age at diagnosis, breast cancer stage, tumor phenotype, study site, education, body mass index (BMI), waist circumference (WC), waist-hip ratio (WHR), diet, physical activity, smoking and alcohol use.

Results: The median follow-up time was 10.8 years since BC diagnosis, with a total of 466 deaths from any cause. Overall, in multivariable models physician diagnosis of diabetes was significantly associated with BC-specific (HR, 1.69; 95% CI 1.14-2.51) and AC mortality (HR, 1.62; 95% CI 1.22-2.19). The association was stronger among Hispanic women for BC-specific mortality (HR, 1.83; 95% CI 1.11-3.03) compared to NHWs (HR, 1.53; 95% CI 0.79-2.95). Further adjustment for BMI, WC and WHR attenuated the point estimates for AC and BC-specific mortality, and the degree of attenuation varied by ethnicity and adiposity measure. For example, WHR was the only measure that significantly attenuated the point estimate among Hispanic women for BC-specific mortality (by 15%). Weight gain between age 30 and referent year was also evaluated; diabetics who gained 25 kg or more had a significant increase in BC-specific mortality (HR, 5.04; 95% CI 1.69-15.07) compared to non-diabetic women. Lastly, BC-specific mortality was significant among women diagnosed with diabetes within five years of BC diagnosis (HR, 2.33, 95% CI 1.31-4.13), compared to non-diabetic women.

Conclusions: Diabetes was associated with BC-specific mortality, particularly among Hispanic women and abdominal adiposity based on WHR was a significant mediator of this association. Future studies of diabetes and BC outcomes among diverse populations should examine changes in WHR among Hispanic BC survivors.

Citation Format: Avonne E. Connor, Kala Visvanathan, Kathy Baumgartner, Richard N. Baumgartner, Stephanie Boone, Lisa M. Hines, Anna R. Giuliano, Esther M. John, Roger K. Wolff, Martha L. Slattery. Ethnic differences in the relationship between diabetes, adiposity measures and breast cancer-specific mortality. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-190. doi:10.1158/1538-7445.AM2015-LB-190