Abstract LB-363: Breastfeeding, parity and risk of mortality among Hispanic and non-Hispanic white women diagnosed with breast cancer: the Breast Cancer Health Disparities Study

Abstract

Abstract Background: A history of breastfeeding was recently shown to be associated with a 48% reduction in breast cancer (BC) mortality, particularly luminal A subtype. Hispanic women have higher parity and are more likely to breastfeed compared to non-Hispanic white (NHW) women. Thus breastfeeding may be an important modifiable prognostic factor for Hispanic women diagnosed with BC. We examined the associations between breastfeeding, parity and BC-specific and overall mortality in Hispanic and NHW BC survivors. Methods: The study population included 2,921 parous women (1,477 Hispanics, 1,444 NHWs) from the San Francisco Bay Area, New Mexico, Utah, Colorado and Arizona with incident, invasive BC diagnosed between April 1995 and April 2002 or between October 1999 and May 2004, depending on study site. Information on reproductive history and lifestyle factors was collected by in-person interview. Hazard ratios (HR) and 95% confidence intervals (CI) were calculated by Cox proportional hazards regression models for overall associations and by estrogen receptor (ER) status, adjusting for study site, ethnicity, age at diagnosis, BC stage, parity, age at first and last full-term pregnancy, pregnancy duration in years, body mass index, waist circumference, and waist-hip ratio. Results: The median follow-up time was 11.2 years since BC diagnosis, with a total of 679 deaths from any cause. A history of breastfeeding was reported by 50.4% of Hispanic cases and 49.6% of NHW cases. Breastfeeding was associated with reduced risk of overall mortality (HR, 0.84; 95% CI 0.72-0.99) adjusting for age, BC stage, parity and ethnicity. The association between breastfeeding and overall mortality was stronger for women diagnosed with estrogen receptor negative (ER-) tumors (HR, 0.69; 95% CI 0.48-0.99). While breastfeeding for ?6 months was not associated with reduced overall mortality (HR, 0.84; 95% CI 0.57-1.25) among women with ER- BC, a reduction of 52% was found for those breastfeeding for <6 months (HR, 0.48; 95% CI 0.29-0.79). Adjusting for age at first and last full term pregnancy, pregnancy duration, and body size measures did not significantly confound the associations with breastfeeding and mortality. Breastfeeding was not associated with BC-specific mortality (HR, 0.91; 95% CI 0.72-1.14); no significant associations between breastfeeding or breastfeeding duration and BC-specific mortality were found in stratified analysis by ER status. Associations between breastfeeding, BC-specific and all-cause mortality were not significant by ethnicity. Parity was not associated with mortality in our study population. Conclusions: Breastfeeding was associated with reduced mortality, particularly among women with ER- tumors in whom there are few modifiable prognostic factors. These results provide another reason to encourage breastfeeding among young women. Citation Format: Avonne E. Connor, Kala Visvanathan, Kathy B. Baumgartner, Richard N. Baumgartner, Stephanie D. Boone, Lisa M. Hines, Anna R. Giuliano, Esther M. John, Roger K. Wolff, Martha L. Slattery. Breastfeeding, parity and risk of mortality among Hispanic and non-Hispanic white women diagnosed with breast cancer: the Breast Cancer Health Disparities Study. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-363.