Breastfeeding and the risk of breast cancer in BRCA1 and BRCA2 mutation carriers
1 Familial Breast Cancer Unit, Women's College Research Institute, 790 Bay Street, Toronto, ON M5G 1N8, Canada
2 Hereditary Cancer Center, Pomeranian Medical University, Ul Polabska 4, 70-115 Szczecin, Poland
3 Department of Preventive Medicine and Public Health, Creighton University School of Medicine, 2500 California Plaza, Omaha, NE 68178 USA
4 BC Cancer Agency, 600 10th Ave. W, Vancouver, BC V5Z 4E6, Canada
5 Programs in Cancer Genetics, Department of Oncology and Human Genetics, McGill University, 3755 Côte Ste-Catherine Montréal, QC H3T 1E2, Canada
6 Epidemiology Research Unit, Research Center of the University of Montreal Hospital Centre (CRCHUM), 3850, rue Saint-Urbain Pavillon Masson, Montreal, QC H2W 1T7, Canada
7 Department of Population Sciences, Beckman Research Institute of City of Hope, 1500 East Duarte Rd., Duarte, CA 91010, USA
8 Division of Gynecologic Oncology, Department of Obstetrics and Gynecology, University of Toronto, 92 College Street, Toronto, ON M5G 1L4, Canada
9 Beth Israel Deaconess Hospital, 330 Brookline, Boston, MA 02215, USA
10 London Regional Cancer Program, 800 Commissioners Rd. E., London, ON N6A 5W9, Canada
11 Division of Human Genetics, The Ohio State University Medical Center, Comprehensive Cancer Center, 2001 Polaris Parkway, Columbus, OH 43240, USA
12 Toronto-Sunnybrook Regional Cancer Center, 2075 Bayview Ave., Toronto, ON M4N 3M5, Canada
13 Genomic Medicine Institute and Center for Personalized Genetic Healthcare, Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195, USA
14 Department of Obstetrics and Gynecology and Comprehensive Cancer Center, Medical University of Vienna, Spitalgasse 23, 1090 Wien, Austria
15 Department of Medicine, University of Toronto, 1 Kings College Circle, Toronto, ON M5S 1A8, Canada
16 Baylor University Medical Center, Hereditary Cancer Risk Program, 3535 Worth Street, Dallas, TX 75246, USA
Breast Cancer Research 2012, 14:R42 doi:10.1186/bcr3138Published: 9 March 2012
Breastfeeding has been inversely related to breast cancer risk in the general population. Clarifying the role of breastfeeding among women with a BRCA1 or BRCA2 mutation may be helpful for risk assessment and for recommendations regarding prevention. We present an updated analysis of breastfeeding and risk of breast cancer using a large matched sample of BRCA mutation carriers.
We conducted a case-control study of 1,665 pairs of women with a deleterious mutation in either BRCA1 (n = 1,243 pairs) or BRCA2 (n = 422 pairs). Breast cancer cases and unaffected controls were matched on year of birth, mutation status, country of residence and parity. Information about reproductive factors, including breastfeeding for each live birth, was collected from a routinely administered questionnaire. Conditional logistic regression was used to estimate the association between ever having breastfed, as well as total duration of breastfeeding, and the risk of breast cancer.
Among BRCA1 mutation carriers, breastfeeding for at least one year was associated with a 32% reduction in risk (OR = 0.68; 95% CI 0.52 to 0.91; P = 0.008); breastfeeding for two or more years conferred a greater reduction in risk (OR = 0.51; 95% CI 0.35 to 0.74). Among BRCA2 mutation carriers, there was no significant association between breastfeeding for at least one year and breast cancer risk (OR = 0.83; 95% CI 0.53 to 1.31; P = 0.43).
These data extend our previous findings that breastfeeding protects against BRCA1-, but not BRCA2-associated breast cancer. BRCA mutation carriers should be advised of the benefit of breastfeeding in terms of reducing breast cancer risk.