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Medline ® Abstract for Reference 12

of 'Epidemiology, risk factors and the clinical approach to ER/PR negative, HER2-negative (Triple-negative) breast cancer'

Parity, lactation, and breast cancer subtypes in African American women: results from the AMBER Consortium.
Palmer JR, Viscidi E, Troester MA, Hong CC, Schedin P, Bethea TN, Bandera EV, Borges V, McKinnon C, Haiman CA, Lunetta K, Kolonel LN, Rosenberg L, Olshan AF, Ambrosone CB
J Natl Cancer Inst. 2014;106(10) Epub 2014 Sep 15.
BACKGROUND: African American (AA) women have a disproportionately high incidence of estrogen receptor-negative (ER-) breast cancer, a subtype with a largely unexplained etiology. Because childbearing patterns also differ by race/ethnicity, with higher parity and a lower prevalence of lactation in AA women, we investigated the relation of parity and lactation to risk of specific breast cancer subtypes.
METHODS: Questionnaire data from two cohort and two case-control studies of breast cancer in AA women were combined and harmonized. Casepatients were classified as ER+ (n = 2446), ER- (n = 1252), or triple negative (ER-, PR-, HER2-; n = 567) based on pathology data; there were 14180 control patients. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated in polytomous logistic regression analysis with adjustment for study, age, reproductive and other risk factors.
RESULTS: ORs for parity relative to nulliparity was 0.92 (95% CI = 0.81 to 1.03) for ER+, 1.33 (95% CI = 1.11 to 1.59) for ER-, and 1.37 (95% CI = 1.06 to 1.70) for triple-negative breast cancer. Lactation was associated with a reduced risk of ER- (OR = 0.81, 95% CI = 0.69 to 0.95) but not ER+ cancer. ER- cancer risk increased with each additional birth in women who had not breastfed, with an OR of 1.68 (95% CI = 1.15 to 2.44) for 4 or more births relative to one birth with lactation.
CONCLUSIONS: The findings suggest that parous women who have not breastfed are at increased risk of ER- and triple-negative breast cancer. Promotion of lactation may be an effective tool for reducing occurrence of the subtypes that contribute disproportionately to breast cancer mortality.
Slone Epidemiology Center at Boston University, Boston, MA (JRP, EV, TNB, LR); University of North Carolina Lineberger Cancer Center, Chapel Hill, NC (MAT, AFO); Roswell Park Cancer Institute, Buffalo, NY (CCH, CBA); University of Colorado Denver School of Medicine, Denver, CO (PS, VB); Rutgers Cancer Institute of New Jersey, New Brunswick, NJ (EVB); Boston University School of Public Health, Boston, MA (CM, KL); Department of Preventive Medicine and Norris Comprehensive Cancer Cencer, University of Southern California Keck School of Medicine, Los Angeles, CA (CAH); Department of Public Health Sciences, University of Hawaii School of Medicine, Honolulu, HI (LNK). jpalmer@bu.edu.