Reduced Risk of Estrogen Receptor–Negative Breast Cancer With Later Age at Menarche in African American Women
In a study reported in the Journal of the National Cancer Institute, Ambrosone et al found that risk of estrogen receptor–negative breast cancer was reduced with later age at menarche in both parous and nulliparous African American women. Greater interval between menarche and first live birth was more clearly associated with increased risk for estrogen receptor–positive than risk for estrogen receptor–negative disease.
Key Findings
The study involved data from 4,426 African American women with breast cancer and 17,474 controls in the AMBER Consortium. Risk of estrogen receptor–negative breast cancer was reduced with later age at menarche among both parous (odds ratio [OR] = 0.62, 95% confidence interval [CI] = 0.48–0.81, for ≥ 15 vs < 11 years) and nulliparous women (OR = 0.56, 95% CI = 0.29–1.10). Age at first live birth had no significant effect on risk for estrogen receptor–negative disease.
Risk of estrogen receptor–positive disease was also reduced by later age at menarche among parous women (OR = 0.70, 95% CI = 0.56–0.86, for ≥ 15 vs < 11 years) but not significantly among nulliparous women (OR = 0.91, 95% CI = 0.59–1.40). There was evidence of increased risk for estrogen receptor–positive disease for first live birth at 25 to 29 years vs ≤ 18 years (OR = 1.21, 95% CI = 1.02–1.44) but for first live birth at older ages.
Interval Between Menarche and First Live Birth
Longer intervals between menarche and first live birth were associated with increased risk of estrogen receptor–positive disease (P = .003 for trend), with an odds ratio of 1.39 (95% CI = 1.08–1.79) for ≥ 20 years vs < 5 years. There was no significant trend for increased risk of estrogen receptor–negative disease with longer interval (P = .33 for trend); however, odds ratios were > 1 for every interval category, and the increase was significant for an interval of 10 to 14 years vs < 5 years (OR = 1.40, 95% CI = 1.10–1.80).
The investigators concluded: “While [estrogen receptor–negative] breast cancer risk was markedly reduced in women with a late age at menarche, there was not a clear pattern of increased risk with longer interval between menarche and [first live birth], as was observed for [estrogen receptor–positive] breast cancer.
These findings indicate that etiologic pathways involving adolescence and pregnancy may differ for [estrogen receptor–negative] and [estrogen receptor–positive] breast cancer.”
Christine B. Ambrosone, PhD, of Roswell Park Cancer Institute, is the corresponding author for the Journal of the National Cancer Institute article.
The study was funded by the National Institutes of Health, Breast Cancer Research Foundation, University Cancer Research Fund of North Carolina.
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