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A Pooled Analysis of Breastfeeding and Breast Cancer Risk by Hormone Receptor Status in Parous Hispanic Women

Sangaramoorthy, Meeraa; Hines, Lisa M.b; Torres-Mejía, Gabrielac; Phipps, Amanda I.d,e; Baumgartner, Kathy B.f; Wu, Anna H.g; Koo, Jocelyna,h; Ingles, Sue A.g; Slattery, Martha L.i; John, Esther M.a,h,j

doi: 10.1097/EDE.0000000000000981
Cancer
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SDC

Background: Data on breastfeeding and breast cancer risk are sparse and inconsistent for Hispanic women.

Methods: Pooling data for nearly 6,000 parous Hispanic women from four population-based studies conducted between 1995 and 2007 in the United States and Mexico, we examined the association of breastfeeding with risk of breast cancer overall and subtypes defined by estrogen receptor (ER) and progesterone receptor (PR) status, and the joint effects of breastfeeding, parity, and age at first birth. We calculated odds ratios (ORs) and 95% confidence intervals (CIs) using logistic regression.

Results: Among parous Hispanic women, older age at first birth was associated with increased breast cancer risk, whereas parity was associated with reduced risk. These associations were found for hormone receptor positive (HR+) breast cancer only and limited to premenopausal women. Age at first birth and parity were not associated with risk of ER− and PR− breast cancer. Increasing duration of breastfeeding was associated with decreasing breast cancer risk (≥25 vs. 0 months: OR = 0.73; 95% CI = 0.60, 0.89; P trend = 0.03), with no heterogeneity by menopausal status or subtype. At each parity level, breastfeeding further reduced HR+ breast cancer risk. Additionally, breastfeeding attenuated the increase in risk of HR+ breast cancer associated with older age at first birth.

Conclusions: Our findings suggest that breastfeeding is associated with reduced risk of both HR+ and ER− and PR− breast cancer among Hispanic women, as reported for other populations, and may attenuate the increased risk in women with a first pregnancy at older ages.

From the aCancer Prevention Institute of California, Fremont, CA

bDepartment of Biology, University of Colorado at Colorado Springs, Colorado Springs, CO

cInstituto Nacional de Salud Pública, Population Health Research Center, Cuernavaca Morelos, Mexico

dDepartment of Epidemiology, University of Washington, Seattle, WA

eEpidemiology Program, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA

fDepartment of Epidemiology and Population Health, School of Public Health & Information Sciences, James Graham Brown Cancer Center, University of Louisville, Louisville, KY

gDepartment of Preventive Medicine, Keck School of Medicine of USC, Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA

hStanford Cancer Institute, Stanford University School of Medicine, Stanford, CA

iDepartment of Medicine, University of Utah, Salt Lake City, UT

jDepartment of Medicine, Division of Oncology, Stanford University School of Medicine, Stanford, CA.

Submitted June 4, 2018; accepted January 28, 2019.

This research was funded by grants CA199343 and CA140002 from the National Cancer Institute. The parent studies were funded by grants CA063446, CA077305, CA078682, CA078762, CA078552, CA078802, and CA164920 from the National Cancer Institute, DAMD17-96-1-6071 from the US Department of Defense Breast Cancer Research Program, 7PB-0068 from the California Breast Cancer Research Program, and SALUD-2002-C01-7462 from Consejo Nacional de Ciencia y Tecnología (CONACyT). The collection of cancer incidence data used in this study was supported by the California Department of Public Health as part of the statewide cancer reporting program mandated by California Health and Safety Code Section 103885; the National Cancer Institute’s Surveillance, Epidemiology and End Results Program under contract HHSN261201000036C awarded to the Cancer Prevention Institute of California; and the Centers for Disease Control and Prevention’s National Program of Cancer Registries, under agreement #1U58 DP000807-01 awarded to the Public Health Institute. The 4-Corners Breast Cancer Study also was supported by the Utah Cancer Registry, which is funded by contract N01-PC-67000 from the National Cancer Institute, with additional support from the State of Utah Department of Health, the New Mexico Tumor Registry, and the Arizona and Colorado cancer registries, funded by the Centers for Disease Control and Prevention National Program of Cancer Registries and additional state support.

Disclosure: The authors report no conflicts of interest.

The contents of this manuscript are solely the responsibility of the authors and do not necessarily represent the official view of the National Cancer Institute or endorsement by the State of California Department of Public Health, the National Cancer Institute, and the Centers for Disease Control and Prevention or their Contractors and Subcontractors. The content of this manuscript does not necessarily reflect the views or policies of the National Cancer Institute or any of the collaborating centers in the Breast Cancer Family Registry (BCFR), nor does mention of trade names, commercial products, or organizations imply endorsement by the US Government or the BCFR.

Data availability: Data may be obtained contingent upon approval by appropriate Institutional Review Boards and study Principal Investigators. The data and computing code may be obtained from the corresponding author on request.

Supplemental digital content is available through direct URL citations in the HTML and PDF versions of this article (www.epidem.com). This content is not peer-reviewed or copy-edited; it is the sole responsibility of the authors.

Correspondence: Esther M. John, Stanford University School of Medicine, 780 Welch Road, Suite CJ250C, Stanford, CA 94304. E-mail: emjohn@stanford.edu.

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