Breast-feeding & Risk Reduction BRCA1/BRCA2

Breast-feeding and the Risk of Breast Cancer in BRCA1 and BRCA2 Mutation Carriers

H. Jernström, J. Lubinski, H. T. Lynch, P. Ghadirian, S. Neuhausen, C. Isaacs, B. L. Weber, D. Horsman, B. Rosen, W. D. Foulkes, E. Friedman, R. Gershoni-Baruch, P. Ainsworth, M. Daly, J. Garber, H. Olsson, P. Sun, S. A. Narod

Affiliations of authors: Jubileum Institute, Department of Oncology, Lund University Hospital, Lund, Sweden (HJ, HO); Hereditary Cancer Center, Pomeranian Medical University, Szczecin, Poland (JL); Department of Preventive Medicine and Public Health, Creighton University School of Medicine, Omaha, NE (HTL); Epidemiology Research Unit, Research Centre, Centre Hospitalier de l'Universitaire Montréal, CHUM Hôtel Dieu, Département de Nutrition, Faculté du Médicine, Québec, Canada (PG); Epidemiology Division, Center for Cancer Genetics Research & Prevention, College of Medicine, University of California, Irvine (SN); Lombardi Cancer Center, Georgetown University Medical Center, Washington, DC (CI); Abramson Family Cancer Research Institute, University of Pennsylvania, Philadelphia (BLW); British Columbia Cancer Agency, Vancouver, British Columbia, Canada (DH); Familial Ovarian Cancer Clinic, Princess Margaret Hospital, Toronto, Ontario, Canada (BR); Departments of Medicine, Human Genetics, and Oncology, McGill University, Montréal, Québec, Canada (WDF); The Suzanne Levy Gertner Oncogenetics Unit, The Chaim Sheba Medical Center, Tel-Hashomer, Israel (EF); The Institute of Genetics, Rambat Medical Center, Haifa, Israel (RGB); London Regional Cancer Center, London, Ontario, Canada (PA); Division of Basic Science and Population Science, Fox Chase Cancer Center, Philadelphia, PA (MD); Department of Adult Oncology, Dana-Farber Cancer Center, Boston, MA (JG); Centre for Research in Women's Health, Women's College Hospital, University of Toronto, Canada (PS, SAN)

Correspondence to: Steven A. Narod, MD, FRCPC, Centre for Research in Women's Health, 790 Bay St., 7th Floor, Toronto, ON, Canada M5G 1N8 (e-mail: steven.narod@sw.ca)

Background: Several studies have reported that the risk of breast cancer decreases with increasing duration of breast-feeding. Whether breast-feeding is associated with a reduced risk of hereditary breast cancer in women who carry deleterious BRCA1 and BRCA2 mutations is currently unknown.

Methods: We conducted a case–control study of women with deleterious mutations in either the BRCA1 or the BRCA2 gene. Study participants, drawn from an international cohort, were matched on the basis of BRCA mutation (BRCA1 [n = 685] or BRCA2 [n = 280]), year of birth (±2 years), and country of residence.

The study involved 965 case subjects diagnosed with breast cancer and 965 control subjects who had no history of breast or ovarian cancer. Information on pregnancies and breast-feeding practices was derived from a questionnaire administered to the women during the course of genetic counseling. Conditional logistic regression analyses were used to estimate odds ratios (ORs) for the risk of breast cancer. All statistical tests were two-sided.

Results: Among women with BRCA1 mutations, the mean total duration of breast-feeding was statistically significantly shorter for case subjects than for control subjects (6.0 versus 8.7 months, respectively; mean difference = 2.7 months, 95% confidence interval [CI] = 1.4 to 4.0; P<.001).

The total duration of breast-feeding was associated with a reduced risk of breast cancer (for each month of breast-feeding, OR = 0.98, 95% CI = 0.97 to 0.99; Ptrend<.001).

Women with BRCA1 mutations who breast-fed for more than 1 year were less likely to have breast cancer than those who never breast-fed (OR = 0.55, 95% CI = 0.38 to 0.80; P = .001), although no such association was seen for BRCA2 (OR = 0.95, 95% CI = 0.56 to 1.59; P = .83).

Conclusions: Women with deleterious BRCA1 mutations who breast-fed for a cumulative total of more than 1 year had a statistically significantly reduced risk of breast cancer.

Journal of the National Cancer Institute, Vol. 96, No. 14, 1094-1098, July 21, 2004

DOI: 10.1093/jnci/djh211

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