By delaying having her first child, a young woman may reduce her risk of triple-negative breast cancer by up to 60%
A younger woman’s risk of an aggressive form of breast cancer may be reduced by up to 60% if she waits at least 15 years following her first menstrual period to give birth to her first child, according to recent research.
The study by Christopher I. Li, MD, PhD, a member of the Public Health Sciences Division at Fred Hutchinson Cancer Research Center, and colleagues is the first to examine the relationship between reproductive factors and breast cancer risk among premenopausal women, who have a higher risk of triple-negative and HER2-overexpressing breast cancer than postmenopausal women.
“We found that the interval between menarche and age at first live birth is inversely associated with the risk of triple-negative breast cancer,” Li said.
More than 1960 Seattle-area women between the ages of 20 and 44 were involved in the study. Among the participants, 1021 had a history of breast cancer and 941 did not. Researchers compared the reproductive histories of the women without a history of breast cancer with those women with estrogen receptor–positive (781), triple-negative (180), and HER2-overexpressing (60) breast cancer.
The study also confirmed what several previous studies that have suggested: that breast-feeding presents a protective effect against triple-negative disease. “Breast-feeding is emerging as a potentially strong protective factor against one of the most aggressive forms of breast cancer,” Li said.
However, the method by which delaying childbirth reduces the risk of this form of breast cancer is unclear, Li said.
The study has particular implications for African-American women, who experience disproportionately high rates of triple-negative disease. The reason for this remains largely unknown. Yet, according to Li, when compared to non-Hispanic white women, African-American women are more likely to start having children at a younger age and are less likely to breast-feed.
“Our observations that delayed childbearing and breast-feeding are protective against triple-negative breast cancer suggest that variations in reproductive histories by race may to some extent explain the higher rates of triple-negative disease in African-American women,” Li said.
“This is an observational study and also one of the first to focus on premenopausal breast cancer and so our results require confirmation and thus should be interpreted with some caution,” Li said.
The findings are published online in Breast Cancer Research and Treatment.