Breast Feeding, Parity and Breast Cancer Subtypes in a Spanish Cohort

Carmen M Redondo,J Esteban Castelao,María Elena Martínez,Máximo Fraga,Ángel Carracedo,Víctor Muñoz Garzón,Ana Alonso García,María Ausencia Tomé,Xuejuan Jiang,Sara Miranda Ponte,Maite Peña Fernández,Manuel Enguix Castelo,Francisco Gude,Manuela Gago-Domínguez

doi:10.1371/journal.pone.0040543

Carmen M Redondo, J Esteban Castelao + Show 12 more

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BackgroundDifferences in the incidence and outcome of breast cancer among Hispanic women compared with white women are well documented and are likely explained by ethnic differences in genetic composition, lifestyle, or environmental exposures.Methodolgy/Principal FindingsA population-based study was conducted in Galicia, Spain. A total of 510 women diagnosed with operable invasive breast cancer between 1997 and 2010 participated in the study. Data on demographics, breast cancer risk factors, and clinico-pathological characteristics were collected. The different breast cancer tumor subtypes were compared on their clinico-pathological characteristics and risk factor profiles, particularly reproductive variables and breastfeeding. Among the 501 breast cancer patients (with known ER and PR receptors), 85% were ER+/PR+ and 15% were ER-&PR-. Among the 405 breast cancer with known ER, PR and HER2 status, 71% were ER+/PR+/HER2- (luminal A), 14% were ER+/PR+/HER2+ (luminal B), 10% were ER−/PR−/HER2- (triple negative breast cancer, TNBC), and 5% were ER−/PR−/HER2+ (non-luminal). A lifetime breastfeeding period equal to or longer than 7 months was less frequent in case patients with TNBC (OR = 0.25, 95% CI = 0.08–0.68) compared to luminal A breast cancers. Both a low (2 or fewer pregnancies) and a high (3–4 pregnancies) number of pregnancies combined with a long breastfeeding period were associated with reduced odds of TNBC compared with luminal A breast cancer, although the association seemed to be slightly more pronounced among women with a low number of pregnancies (OR = 0.09, 95% CI = 0.005–0.54).Conclusions/SignificanceIn case-case analyses with the luminal A cases as the reference group, we observed a lower proportion of TNBC among women who breastfed 7 or more months. The combination of longer breastfeeding duration and lower parity seemed to further reduce the odds of having a TNBC compared to a luminal A breast cancer.

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In the US, breast cancer impacts each racial group differently [1,2,3,4]
It has been reported that women diagnosed with estrogen receptor-positive (ER+)/progesterone receptor-positive (PR+) tumors are more responsive to hormonal treatment and have a better prognosis than those diagnosed with estrogen receptornegative (ER-)/progesterone receptor negative (PR-) tumors, suggesting etiologic heterogeneity of hormone-receptor defined subtypes of breast cancer [8,9]
We describe the characteristics of breast cancer subtypes defined by ER, PR and HER2 receptor status and assessed the associations between reproductive factors and breastfeeding and tumor subtypes in a case series of female breast cancer patients from Galicia, a region located in the northwest part of Spain, whose history has been defined by mass emigration to Latin America [13]

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Introduction

In the US, breast cancer impacts each racial group differently [1,2,3,4]. Compared with non-Hispanic White (NHW) women, Hispanic women have a lower incidence rate of breast cancer, once diagnosed with this disease they are more likely to die from it [5]. Studies [6,7] have found that despite equal access to health care services, differences persist in the presentation of Hispanic women with breast cancer compared with NHW women, suggesting a biologic basis for the racial/ethnic differences. Differences in the incidence and outcome of breast cancer among Hispanic women compared with white women are well documented and are likely explained by ethnic differences in genetic composition, lifestyle, or environmental exposures. The different breast cancer tumor subtypes were compared on their clinico-pathological characteristics and risk factor profiles, reproductive variables and breastfeeding. A lifetime breastfeeding period equal to or longer than 7 months was less frequent in case patients with TNBC (OR = 0.25, 95% CI = 0.08–0.68) compared to luminal A breast cancers.

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