Reproductive factors and the risk of triple-negative breast cancer in white women and African-American women: a pooled analysis

Abstract

BackgroundEarly 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).MethodsWe 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.ResultsTNBC risk decreased with increasing duration of breastfeeding (P trend = 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).ConclusionsOur data indicate that breastfeeding decreases the risk of TNBC, especially for younger African-American women.

Reproductive Risk Factors Associated with Breast Cancer Molecular Subtypes among Young Women in Northern China

“…Similarly, we observed that parity reduced the risk of luminal A and luminal B tumor subtypes in both young and older women. Our findings in BCYW were in accordance with previous case-control studies in young women (<45 years) [31,32]. However, we did not observe that this association differed significantly according to age (P > 0:05).…”

“…BioMed Research International studies reported the opposite [32][33][34], as confirmed by our results. While parity has been confirmed to be related to a decreased risk of luminal BCYW, its relationship with TNBC remains uncertain.…”

Reproductive history, breast‐feeding and risk of triple negative breast cancer: The Breast Cancer Etiology in Minorities (BEM) study

“…14,20,21 Our finding of a 48% reduction in TNBC risk for younger parous women who breast-fed for 24 months is consistent with other studies [22][23][24][25] and a pooled analysis in African American and white women 26 that reported 40-50% risk reductions associated with breast-feeding for 12 months. Consistent with our results, the pooled analysis 26 and other studies 24,27-29 also failed Adjusted for base covariates, including age (continuous), study (AABCS, SFBCS and NC-BCFR), time period (1995-1999, 2000-2004 and 2005-2009) and race/ethnicity (African American, Asian American, Hispanic and non-Hispanic white). 2 Additionally adjusted for education (some high school or less, high school degree, vocational/technical school or some college and college or higher degree), family history of breast cancer in first-degree relatives (yes or no), height (quartiles) and oral contraceptive use (never, former and current).…”

Breast cancer statistics, 2017, racial disparity in mortality by state

“…For example, although overall rates of HR-negative/HER2-positive breast cancers in API women are similar to the rates in other groups, an analysis of California women by Asian ethnic subgroup reported that Korean, Filipina, Chinese, and Southeast Asian women had a higher risk of HR-negative/HER2-positive breast cancers compared with NHW women, whereas Japanese and American Indian women had lower risk for this subtype. 17 Racial and ethnic differences in breast cancer subtypes may reflect variation in the prevalence of breast cancer risk factors, particularly reproductive factors, which are most strongly associated with HR-positive breast cancers 15,18 but also appear to reflect ancestry-related genetic variations. [19][20][21] Stage distribution and survival Racial and ethnic variations in breast cancer stage at diagnosis and 5-year cause specific survival are shown in Figure 4.…”