Cancer
Breastfeeding reduces risk of breast cancer for women
By Sue Mueller
Apr 16, 2007 - 8:06:32 PM

Breastfeeding can reduce the risk of breast cancer for women who have their first childbirth after the age of 25, according to a study presented at a news conference on Monday April 16 at the 2007 annual meeting of the American Association for Cancer Research held in Los Angeles.

The study led by researchers at the University of Southern California suggests that breastfeeding can offset the increased risk of breast cancer in women associated with their late childbirth.

“Breastfeeding may have a protective effect that negates the increased risk of breast cancer associated with late pregnancies,” says Giske Ursin, M.D., Ph.D, associate professor of preventive medicine at the Keck School of Medicine of the University of Southern California.

“As more women may choose to delay pregnancy until after 25, it is important to note that breastfeeding provides protection against both estrogen and progesterone receptor positive and negative tumors.”

Having a first full-term pregnancy before the age of 25 and having many children protect only against the type of breast cancers that express estrogen and progesterone receptors. The factors do not have an effect on rare tumors that do not have the noted receptors. Breastfeeding, however, appears to protect against both types of breast tumors, Ursin says.

The researchers came to the conclusion after analyzing data for women aged 55 and older who participated in the Women’s Contraceptive and Reproductive Experiences (CARE) Study including 995 invasive breast cancer patients.

The researchers analyzed the associations among their age at first birth, their breastfeeding history and hormone receptor status.

Previous results from the Women’s CARE Study have already shown that women with their first pregnancy occurring at an age younger than 25 and having many children (four or more pregnancies) have a reduced risk of breast cancer, Ursin says.

The new study found that breastfeeding appears to have a protective effect against breast cancer regardless of the age at which women had their first pregnancy, Ursin says.

Having many children can only protect those who had their first pregnancy before the age of 25 years.  First birth often given after the age of 25 in the United States is linked with an increased risk of hormone receptor negative breast cancer.

“Evidence suggests that women who have children after age 25 can reduce their risk of breast cancer by choosing to breastfeed,” Ursin says.