Menstrual and reproductive characteristics and breast cancer risk by hormone receptor status and ethnicity: The Breast Cancer Etiology in Minorities study. Issue 7 (29th February 2020)

• Record Type: Journal Article
• Authors: John, Esther M.; Phipps, Amanda I.; Hines, Lisa M.; Koo, Jocelyn; Ingles, Sue A.; Baumgartner, Kathy B.; Slattery, Martha L.; Wu, Anna H.
• Is Part Of: International journal of cancer. Volume 147:Issue 7(2020)
• Page Start: 1808
• Page End: 1822
• Publication Date: 2020-02-29
• Subjects: breast cancer -- epidemiology -- estrogen receptor status -- progesterone receptor status -- ethnicity -- reproductive history; Cancer -- Periodicals; Cancer -- Prevention -- Periodicals; 616.994
• DOI: 10.1002/ijc.32923
• Languages: English
• ISSNs: 0020-7136

Abstract

Abstract : We pooled multiethnic data from four population‐based studies and examined associations of menstrual and reproductive characteristics with breast cancer (BC) risk by tumor hormone receptor (HR) status [defined by estrogen receptor (ER) and progesterone receptor (PR)]. We estimated odds ratios and 95% confidence intervals using multivariable logistic regression, stratified by age (<50, ≥50 years) and ethnicity, for 5, 186 HR+ (ER+ or PR+) cases, 1, 365 HR− (ER− and PR−) cases and 7, 480 controls. For HR+ BC, later menarche and earlier menopause were associated with lower risk in non‐Hispanic whites (NHWs) and Hispanics, and higher parity and longer breast‐feeding were associated with lower risk in Hispanics and Asian Americans, and suggestively in NHWs. Positive associations with later first full‐term pregnancy (FTP), longer interval between menarche and first FTP and shorter time since last FTP were limited to younger Hispanics and Asian Americans. Except for nulliparity, reproductive characteristics were not associated with risk in African Americans. For HR− BC, lower risk was associated with later menarche, except in African Americans and older Asian Americans and with longer breast‐feeding in Hispanics and Asian Americans only. In younger African Americans, HR− BC risk associated with higher parity (≥3 vs . 1 FTP) was increased fourfold in women who never breast‐fed, but not in those with a breast‐feeding history, suggesting that breast‐feeding may mitigate the adverse effect of higher parity in younger African American women. Further work needs to evaluate why menstrual and reproductive risk factors vary in importance according to age and ethnicity. Abstract : What's new? To examine how breast cancer risk varies among ethnic groups, these authors pooled data from 4 population‐based studies. They analyzed the relationship between menstrual and reproductive characteristics and breast cancer risk by hormone receptor status. In non‐Hispanic whites, Hispanics, and Asian‐Americans, associations were as expected. Characteristics such as later onset of menstruation, earlier menopause, higher parity, and longer breastfeeding were associated with lower risk of HR+ cancer in these groups. Among African Americans, however, most menstrual and reproductive characteristics showed no association with breast cancer risk, in contrast to a previous study. They did detect an increased risk for HR‐ cancer in African‐American women with higher parity who never breast‐fed.