Reproductive factors and the risk of triple-negative breast cancer in white women and African-American women: a pooled analysis
Published Date:Jan 13 2017
Source:Breast Cancer Res. 19.
Pubmed Central ID:PMC5237290
Funding:N01 PC067010/PC/NCI NIH HHS/United States
Y01 HD007022/HD/NICHD NIH HHS/United States
N01 CN065064/CN/NCI NIH HHS/United States
R03 CA188549/CA/NCI NIH HHS/United States
K05 CA136967/CA/NCI NIH HHS/United States
R01 CA074847/CA/NCI NIH HHS/United States
P01 CA017054/CA/NCI NIH HHS/United States
N01PC35139/CA/NCI NIH HHS/United States
Early age at menarche, nulliparity, late age at first completed pregnancy, and never having breastfed, are established breast cancer risk factors. However, among breast cancer subtypes, it remains unclear whether all of these are risk factors for triple-negative breast cancer (TNBC).
We evaluated the associations of these reproductive factors with TNBC, in 2658 patients with breast cancer (including 554 with TNBC) and 2448 controls aged 20–64 years, who participated in one of the three population-based case-control studies: the Women’s Contraceptive and Reproductive Experiences Study, the Women’s Breast Carcinoma in situ Study, or the Women’s Learning the Influence of Family and Environment Study. We used multivariable polychotomous unconditional logistic regression methods to conduct case-control comparisons among breast cancer subtypes defined by estrogen receptor, progesterone receptor, and human epidermal growth factor receptor-2 expression status.
TNBC risk decreased with increasing duration of breastfeeding (Ptrend = 0.006), but age at menarche, age at first completed pregnancy, and nulliparity were not associated with risk of TNBC. Parous women who breastfed for at least one year had a 31% lower risk of TNBC than parous women who had never breastfed (odds ratio, OR = 0.69; 95% confidence interval, CI = 0.50–0.96). The association between breastfeeding and risk of TNBC was modified by age and race. Parous African-American women aged 20–44 years who breastfed for 6 months or longer had an 82% lower risk of TNBC than their counterparts who had never breastfed (OR = 0.18, 95% CI = 0.07–0.46).
Our data indicate that breastfeeding decreases the risk of TNBC, especially for younger African-American women.
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