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

• Published in: JNCI : Journal of the National Cancer Institute Vol. 96; no. 14; pp. 1094 - 1098
• Main Authors: Jernström, H., Lubinski, J., Lynch, H. T., Ghadirian, P., Neuhausen, S., Isaacs, C., Weber, B. L., Horsman, D., Rosen, B., Foulkes, W. D., Friedman, E., Gershoni-Baruch, R., Ainsworth, P., Daly, M., Garber, J., Olsson, H., Sun, P., Narod, S. A.
• Format: Journal Article
• Language: English
• Published: Cary, NC Oxford University Press 21.07.2004; Oxford Publishing Limited (England)
• Subjects: Adult; Aged; Biological and medical sciences; Breast cancer; Breast Feeding; Breast Neoplasms - genetics; Breast Neoplasms - prevention & control; Breastfeeding & lactation; Cancer and Oncology; Cancer och onkologi; Case-Control Studies; Clinical Medicine; Female; Genes, BRCA1; Genes, BRCA2; Genetic Predisposition to Disease; Gynecology. Andrology. Obstetrics; Heterozygote; Humans; Klinisk medicin; Logistic Models; Mammary gland diseases; Medical and Health Sciences; Medical research; Medical sciences; Medicin och hälsovetenskap; Middle Aged; Mutation; Odds Ratio; Parity; Risk Assessment; Time Factors; Tumors; Israel; Asia; North America; Europe; America; Human; Breast cancer; Malignant tumor; Breast feeding; Epidemiology; Mammary gland diseases; Cancerology; Risk factor; Genetics; Adult; Female; Mutation; BRCA1 gene; Public health; Tumor suppressor gene
• ISSN: 0027-8874; 1460-2105; 1460-2105
• DOI: 10.1093/jnci/djh211

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.