(HealthDay News) — Age at menarche could play a role in development of estrogen receptor-negative (ER−) breast cancers among African-American women, according to a study published in the September issue of the Journal of the National Cancer Institute.

Christine B. Ambrosone, PhD, from the Roswell Park Cancer Institute in Buffalo, NY, and colleagues analyzed data gathered from the AMBER Consortium (4,426 African-American women with breast cancer and 17,474 controls). The authors performed polytomous logistic regression to estimate odds ratios (ORs) for ages at menarche and first live birth (FLB), and the interval between, in relation to ER+ and ER− breast cancer.

The researchers found that risk of ER− breast cancer was reduced with later age at menarche among both parous and nulliparous women (≥15 vs. <11 years; ORs, 0.62 [95% confidence interval, 0.48–0.81] and 0.56 [95% confidence interval, 0.29–1.10], respectively), with no effect of age at FLB. The inverse association was weaker among nulliparous women with ER+ breast cancer. Longer intervals between menarche and FLB were associated with increased risk of ER+ breast cancer in a dose-response manner (OR for 20 year interval, 1.39; Ptrend=0.003); however, ER− risk was only increased for intervals up to 14 years (Ptrend=0.33).

“These findings indicate that etiologic pathways involving adolescence and pregnancy may differ for ER− and ER+ breast cancer,” the authors write.

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