title: Epidemiology of basal-like breast cancer.
abstract: Risk factors for the newly identified "intrinsic" breast cancer subtypes (luminal A, luminal B, basal-like and human epidermal growth factor receptor 2-positive/estrogen receptor-negative) were determined in the Carolina Breast Cancer Study, a population-based, case-control study of African-American and white women. Immunohistochemical markers were used to subtype 1,424 cases of invasive and in situ breast cancer, and case subtypes were compared to 2,022 controls. Luminal A, the most common subtype, exhibited risk factors typically reported for breast cancer in previous studies, including inverse associations for increased parity and younger age at first full-term pregnancy. Basal-like cases exhibited several associations that were opposite to those observed for luminal A, including increased risk for parity and younger age at first term full-term pregnancy. Longer duration breastfeeding, increasing number of children breastfed, and increasing number of months breastfeeding per child were each associated with reduced risk of basal-like breast cancer, but not luminal A. Women with multiple live births who did not breastfeed and women who used medications to suppress lactation were at increased risk of basal-like, but not luminal A, breast cancer. Elevated waist-hip ratio was associated with increased risk of luminal A in postmenopausal women, and increased risk of basal-like breast cancer in pre- and postmenopausal women. The prevalence of basal-like breast cancer was highest among premenopausal African-American women, who also showed the highest prevalence of basal-like risk factors. Among younger African-American women, we estimate that up to 68% of basal-like breast cancer could be prevented by promoting breastfeeding and reducing abdominal adiposity.
authors.affiliation: Department of Epidemiology, CB #7435, School of Public Health, University of North Carolina, Chapel Hill, NC 27599-7435, USA. millikan@email.unc.edu
authors.forename: Robert C
authors.initials: RC
authors.lastname: Millikan
authors.forename: Beth
authors.initials: B
authors.lastname: Newman
authors.forename: Chiu-Kit
authors.initials: CK
authors.lastname: Tse
authors.forename: Patricia G
authors.initials: PG
authors.lastname: Moorman
authors.forename: Kathleen
authors.initials: K
authors.lastname: Conway
authors.forename: Lynn G
authors.initials: LG
authors.lastname: Dressler
authors.forename: Lisa V
authors.initials: LV
authors.lastname: Smith
authors.forename: Miriam H
authors.initials: MH
authors.lastname: Labbok
authors.forename: Joseph
authors.initials: J
authors.lastname: Geradts
authors.forename: Jeannette T
authors.initials: JT
authors.lastname: Bensen
authors.forename: Susan
authors.initials: S
authors.lastname: Jackson
authors.forename: Sarah
authors.initials: S
authors.lastname: Nyante
authors.forename: Chad
authors.initials: C
authors.lastname: Livasy
authors.forename: Lisa
authors.initials: L
authors.lastname: Carey
authors.forename: H Shelton
authors.initials: HS
authors.lastname: Earp
authors.forename: Charles M
authors.initials: CM
authors.lastname: Perou
mesh_terms: D044383:Black People; D015992:Body Mass Index; D049628:Body Size; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000235:genetics*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008593:Menopause; D016017:Odds Ratio; D017698:Postmenopause; D017697:Premenopause; D012306:Risk; D012307:Risk Factors; D044465:White People; D001741:Black or African American