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LOS ANGELES -- Breastfeeding appears to cancel out the significantly added risk of hormone-negative breast cancer for women who are nulliparous until after age 25, researchers reported here.
LOS ANGELES, April 19 -- Breastfeeding appears to cancel out the significantly added risk of hormone-negative breast cancer for women who are null1parous until after age 25, researchers reported here.
The protective effect of breastfeeding extends to breast tumors that are hormone-receptor-positive as well, said Giske Ursin, M.D., Ph.D., of the University of Southern California in Los Angeles at the American Association for Cancer Research meeting here.
Regardless of maternal age, the protective effective of parity on hormone-positive tumors was only seen among women who breastfed (P for trend= 0.001), not women who never breastfed (P for trend=0.29).
"We believe that breastfeeding should be encouraged for all women," she said. But she cautioned that while she was reporting an association between breastfeeding and reduced cases of breast cancer "we cannot say that breastfeeding is a direct cause and effect for protecting women against breast cancer."
The association emerged from analysis of data from 995 women with incident invasive breast cancer and 1,498 controls.
Dr. Ursin collected age of first pregnancy, parity, and breastfeeding history from both cases and controls. All women were 55 or older and all were participants in the Women's Contraceptive and Reproductive Experiences (CARE) study, a multicenter case-control study of breast cancer in white and African American women.
Seven hundred and twenty-eight women had estrogen- receptor/progesterone-receptor positive tumors and 267 had hormone-negative cancers.
Among the findings: