Abstract C89: Ages at menarche and first birth and estrogen receptor status among African American and European American women with breast cancer

Introduction. Early age at menarche, which has declined in the last two centuries, is an established risk factor for breast cancer (BC). Age at menarche has been consistently younger for women of African ancestry (AA) than for European-Americans (EA), and could be associated with the higher incidence of tumors that are ER negative (-) among AAs. Age at first live birth, also earlier for AAs, and the interval between menarche and first birth may also have differential effects on breast tumor characteristics. Methods. The Women9s Circle of Health Study (WCHS) is a case-control study of BC in EA and AA women conducted in metropolitan New York City (NYC) and several counties in eastern New Jersey (NJ). Eligible cases were English speaking women with incident BC who self-identified as AA or EA, were 20-75 years of age at diagnosis, and had no previous history of cancer other than non-melanoma skin cancer. Age and race-matched controls were identified using random digit dialing (RDD) in both NY and NJ, and from communities in NJ through churches and health fair events. In-home interviews were conducted and pathology reports abstracted for data on hormone receptors. Included in these analyses were data from 786 AA and 538 EA women with BC and 1015 AA and 715 EA controls. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were estimated using unconditional logistic regression to examine associations between age at menarche, age at first live birth, and the interval between those ages and odds of ER+ and ER- breast tumors. Full models were adjusted for factors associated with the exposure, risk of BC in our data, and potential confounders. Results. Higher proportions of AA women experienced menarche before age 11 (13% for cases; 11% for controls) than EAs (10% for cases, 8% for controls). There were also higher proportions of AA women with first birth before age 18 (19% for cases; 21% for controls) than EA women (2% for both cases and controls). In multivariable analysis, later age at menarche was associated with reduced risk of both ER+ and ER- BC in AA women, although associations were more pronounced for ER- disease (3rd tertile OR=0.54; 95% CI, 0.34-0.86) than for ER+ BC (3rd tertile OR=0.75; 95%CI, 0.52-1.07). Among EA women, associations were weaker and non-significant. ORs for age at first live birth were similar for ER- and ER+ BC in AA women, and were essentially null. In EA women, later age at first live birth was non-significantly associated with increased risk of both ER+ and ER- BC. Compared to women with less than a 5 year interval between menarche and first pregnancy, there was significantly increased risk of ER- BC for AA women who had up to a 14 year interval (OR=1.93; CI, 1.19-3.12), with non-significant associations for longer intervals, and weaker associations for ER+ BC. In EA women, longer intervals between menarche and first live birth were associated with elevated risk of ER- but not ER+ BC. Conclusions. Associations between menstrual and reproductive characteristics and BC differed between AA and EA women and according to ER status. In AA women, there was greater reduced risk of ER- BC with later age at menarche, and increased risk of ER- BC with longer intervals between menarche and first live birth. There is a growing body of literature indicating that reproductive characteristics, such as parity, are differentially associated with ER status; these data further suggest that additional hormonal exposures, such as age at menarche and time to first pregnancy, also influence the development of more aggressive, ER- tumors, particularly in AA women. Note: The author block has been changed and no longer matches the print Proceedings. Citation Format: Christine B. Ambrosone, Gary Zirpoli, Chi-Chen Hong, Lina Jandorf, Dana H. Bovbjerg, Elisa V. Bandera. Ages at menarche and first birth and estrogen receptor status among African American and European American women with breast cancer. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr C89. doi:10.1158/1538-7755.DISP13-C89