Breastfeeding :: Breastfeeding may help protect women against breast cancer

Research has shown there is a connection between reproductive factors?such as age at first birth, number of births, and breastfeeding?and a woman?s risk of breast cancer.

Yet to be established is how these factors interact, and whether they have differing effects on risk for breast cancers that are estrogen and progesterone receptor positive (ERPR-positive) versus those that are not (ERPR-negative).

A new study by a team of researchers in the U.S. and Australia suggests that breastfeeding may help protect women against both subtypes.

“Our previous research had shown differing effects of these reproductive factors on ERPR-positive and ERPR-negative breast cancers, and we wanted to understand them better,” said study co-author Giske Ursin, M.D., Ph.D., associate professor in the Department of Preventive Medicine at the University of Southern California?s Keck School of Medicine. “Our most important finding here is that breastfeeding seems to modify the increased risk that comes from having children later in life.”

The study looked at 995 women with invasive breast cancer (729 ERPR-positive, 267 ERPR-negative), and 1498 controls, aged 55 years or older who participated in the Women?s Contraceptive and Reproductive Experiences Study, a multicenter study of breast cancer in white and African-American women. The researchers considered women?s age at first birth, the number of births ? referred to as parity ? and whether or not they had ever breastfed.Women with a first birth before age 25 had 41percent lower relative risk of developing ERPR-positive breast cancer than women with no births; this protective effect did not hold true for women who gave birth at or after 25. The latter group also had double the risk of developing ERPR-negative cancers. “What we find is that early age at first birth protects against ERPR-positive cancer, but not receptor-negative,” Ursin said.

More notable, researchers said, was their finding related to age at first birth and parity. Breastfeeding was protective for both subtypes, regardless of when a woman gave birth.

“The protective effect of parity on ERPR-positive cancers was seen only among women who breastfed, but not among those who never breastfed,” said Ursin. “And for women giving birth after age 25, parity was associated with increased risk for both types of breast cancer only in women who had never breastfed.”

The researchers concluded that breastfeeding may lessen the increased risk that comes from having children later in life. According to Ursin, breastfeeding may act through different hormonal mechanisms than early age at first birth and parity.

For now, the study suggests that women who delay childbearing should consider breastfeeding when they do have children. “We suspect that women can reduce the increased risk that comes with later childbearing by choosing to breastfeed,” Ursin said.

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