Delaying childbirth may reduce the risk of an aggressive form of breast cancer in younger women, study suggests

http://www.fhcrc.org/en/news/releases/2012/12/delay-childbirth-reduce-risk-breast-cancer.html

Dec. 12, 2012 – Younger women who wait at least 15 years after their first menstrual period to give birth to their first child may reduce their risk of an aggressive form of breast cancer by up to 60 percent, according to a Fred Hutchinson Cancer Research Center study. The findings, by Christopher I. Li, M.D., Ph.D., a member of the Public Health Sciences Division at Fred Hutch, are published online in Breast Cancer Research and Treatment.

“We found that the interval between menarche and age at first live birth is inversely associated with the risk of triple-negative breast cancer,” Li said. While relatively uncommon, triple-negative breast cancer is a particularly aggressive subtype of the disease that does not depend on hormones such as estrogen to grow and spread. This type of cancer, which accounts for only 10 percent to 20 percent of all breast cancers, does not express the genes for estrogen receptor (ER), progesterone receptor (PR) or HER2/neu and therefore does not respond to hormone-blocking drugs such as Tamoxifen.

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The study also confirmed several previous studies that have suggested that breast-feeding confers a protective effect against triple-negative disease. “Breast-feeding is emerging as a potentially strong protective factor against one of the most aggressive forms of breast cancer,” Li said.

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Previous research has shown, however, that the risk of the most common subtype of breast cancer, ER positive, is decreased among women who’ve had a full-term pregnancy and have breast-fed. The reason for this, researchers believe, is that the hormones of pregnancy induce certain changes in the cellular structure of the breast that seem to make the tissue less susceptible to this type of cancer.

The study has particular implications for African-American women, who experience disproportionately high rates of triple-negative disease. While the reason for this remains largely unknown, on a population level reproductive characteristics are known to vary by race, and compared to non-Hispanic white women, African-American women are more likely to start having children at a younger age and are less likely to breast-feed, Li said.

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