This summary table contains detailed information about research studies. Summary tables offer an informative look at the science behind many breast cancer guidelines and recommendations. However, they should be viewed with some caution. In order to read and interpret research tables successfully, it is important to understand some key concepts. Learn how to read a research table.
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Introduction: There is solid evidence breastfeeding can lower the risk of breast cancer. Findings from two large meta-analyses that combined the results from many studies showed women who breastfed had a lower risk of breast cancer compared to those who had not [1,2].
A meta-analysis of five case-control studies found breastfeeding reduced the risk of both hormone receptor-positive (ER+/PR+) and hormone receptor-negative (ER-/PR-) breast cancers [3].
Learn about the strengths and weaknesses of different types of studies.
See how this risk factor compares with other risk factors for breast cancer.
Study selection criteria: Large pooled and meta-analyses.
Table note: Relative risk above 1 indicates increased risk. Relative risk below 1 indicates decreased risk.
Study
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Study Population
(number of participants)
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Relative Risk of Breast Cancer in Women who Breastfed Compared to Women who Did Not
RR (95% CI)
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Premenopausal
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Postmenopausal
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Pooled and meta-analyses
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Bernier et al. [1]*
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70,777
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0.76 (0.66-0.87)
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0.83 (0.68-1.01)
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CGHFBC [2]†
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147,275
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0.94‡ Sig
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Sig = Statistically significant.
* Case-control studies only.
† Includes all case-control studies and some, but not all, major cohort studies. For cohort studies not included, the combined RR for ever versus never having breastfed was 0.93 (0.87-1.00).
‡ For one year of breastfeeding.
References
1. Bernier MO, Plu-Bureau G, Bossard N, et al. Breast feeding and risk of breast cancer: a meta-analysis of published studies. Hum Reprod Update. 6(4):374-386, 2000.
2. Collaborative Group on Hormonal Factors in Breast Cancer. Breast cancer and breast feeding: collaborative reanalysis of individual data from 47 epidemiological studies in 30 countries, including 50,302 women with breast cancer and 96,973 women without the disease. Lancet 20:187-195, 2002.
3. Ma H, Bernstein L, Pike MC, Ursin G. Reproductive factors and breast cancer risk according to joint estrogen and progesterone receptor status: a meta-analysis of epidemiological studies. Breast Cancer Res. 19;8(4):R43, 2006.
Updated 07/06/11
