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CancerConnect News:  Breastfeeding could cut the chance of developing breast cancer by up to one fifth according to researchers sharing the results of a major clinical study presented at the 2014 San Antonio Breast Cancer Symposium.1

Previous studies have suggested that breastfeeding has a protective effect against the development of breast cancer, but the impact appeared relatively small.2 In order to better evaluate the relationship between breast feeding and the subsequent development of breast cancer, researchers examined 27 studies performed over three decades, involving 750,000 women, 36,000 of whom developed breast cancer.

The meta-analysis of these 27 studies found that breast feeding reduced the risks of invasive breast cancers by approximately10%. The research, led by American cancer charities with the Washington University School of Medicine and Mount Sinai Hospital, found that breast feeding not only protected against common types of breast cancer but against the more aggressive triple-negative breast cancer as well.

The study did not determine the optimum duration of breast feeding in order to reduce the risk of developing breast cancer; but according to the study authors, the risks seemed to decrease the longer women continued. Broader uptake of breast feeding and completing up to 12 weeks of breast feeding for each baby can significantly reduce the subsequent risk of breast cancer.

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Learn more about the management of breast cancer

It has long been held that hormonal changes that take place during pregnancy and lactation are responsible for the reduction in breast cancer risk.Women do not usually ovulate while producing milk and this is understood to protect against cancer of the breast and ovaries. Doctors agree that breastfeeding is a powerful strategy to reduce the risk of breast cancer and it is fairly well accepted that breast feeding is healthy for the baby as well.


  1. Weiss M, Liu Y, Boffetta P, Colditz G, Jemel A, Islami F. Association between breastfeeding and breast cancer risk by receptor status: A meta-analysis. Presented at the 2014 San Antonio Breast Cancer Symposium. December 9-13, 2014. San Antonio, Texas. Abstract P5-13-01.
  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. 2002; 20:187-195.

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