Breastfeeding can offset the increased risk of invasive breast cancer for women who had their first full-term pregnancy after the age of 25, a study led by researchers at the University of Southern California (USC) suggests.
The findings of the study were 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.
"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."
While having a first full-term pregnancy before the age of 25 and having many children protect against the type of breast cancers that express estrogen and progesterone receptors, these factors do not protect against the rarer tumors that do not have these receptors. Breastfeeding, however, appears to protect against both types of breast tumors, Ursin says.
Researchers analyzed data for women aged 55 and older, including 995 invasive breast cancer patients, who participated in the Women's Contraceptive and Reproductive Experiences (CARE) Study. The women varied by their age at first birth, their breastfeeding history and hormone receptor status.