(HealthDay News) — Age at menarche could play a role in development of estrogen receptor-negative breast cancers among African-American women, according to a study published in the Journal of the National Cancer Institute.
Christine B. Ambrosone, PhD, from the Roswell Park Cancer Institute in Buffalo, New York., and colleagues analyzed data gathered from the AMBER Consortium (4,426 African-American women with breast cancer and 17,474 controls).
The researchers performed polytomous logistic regression to estimate odds ratios (ORs) for ages at menarche and first live birth, and the interval between, in relation to ER-positive and ER-negative breast cancer.
Risk for ER-negative breast cancer was reduced with later age at menarche among both parous and nulliparous women (≥15 vs. <11 years; ORs, 0.62 [95% CI, 0.48-0.81] and 0.56 [95% CI, 0.29-1.10], respectively), with no effect of age at first live birth. The inverse association was weaker among nulliparous women with ER-positive breast cancer.
Longer intervals between menarche and first live birth were associated with increased risk for ER-positive breast cancer in a dose-response manner (OR for 20 year interval, 1.39; Ptrend=.003); however, ER-negative risk was only increased for intervals up to 14 years (Ptrend=.33).
“These findings indicate that etiologic pathways involving adolescence and pregnancy may differ for ER-negative and ER-positive breast cancer,” the researchers wrote.