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Breast Cancer Risk Reduced When Women Breast-feed

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Risk for ER/PR-negative breast cancer increased when not breast-feeding following childbirth

The risk for estrogen receptor–negative and progesterone receptor–negative breast cancer is reduced with breast-feeding, according to results presented at the 11th Annual American Association for Cancer Research International Conference on Frontiers in Cancer Prevention Research.

“We found an increased risk for estrogen receptor- and progesterone receptor- (ER/PR) negative breast cancer in women who do not breast-feed, but in women who have children and breast-feed, there is no increased risk,” said Meghan Work, MPH, doctoral student in the department of epidemiology at Columbia University’s Mailman School of Public Health in New York, NY

The researchers assessed the relationship between reproductive risk factors (the number of children a woman delivers, breast-feeding, and oral contraceptive use) and ER/PR-negative breast cancer. According to Work, ER/PR-negative breast cancer often affects younger women and has a poor prognosis.

For the study, data from 3 sites of the Breast Cancer Family Registry were used. They include women with and without breast cancer from the United States, Canada, and Australia. Work and colleagues included 4011 women with breast cancer and 2997 population-based controls.

The results showed that having 3 or more children without breast-feeding was associated with an increased risk for ER/PR-negative breast cancer.

“Women who had children but did not breast-feed had about 1.5 times the risk for ER/PR-negative breast cancer when compared with a control population,” Work said. “If women breast-fed their children, there was no increased risk for ER/PR-negative cancer.”

Furthermore, study results indicated that, with the exception of those formulations available before 1975, oral contraceptive use was not associated with ER/PR-negative cancer risk. “These earlier formulations contained higher doses of estrogen and progestin than more recent versions,” Work said.

Previous study findings have also revealed a breast-feeding benefit in triple-negative breast cancer. “This is particularly important as breast-feeding is a modifiable factor that can be promoted and supported through health policy,” Work said.

Source: AACR.