Epidemiology of basal-like breast cancer.
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.
Millikan
Robert C
RC
Department of Epidemiology, CB #7435, School of Public Health, University of North Carolina, Chapel Hill, NC 27599-7435, USA. millikan@email.unc.edu
Newman
Beth
B
Tse
Chiu-Kit
CK
Moorman
Patricia G
PG
Conway
Kathleen
K
Dressler
Lynn G
LG
Smith
Lisa V
LV
Labbok
Miriam H
MH
Geradts
Joseph
J
Bensen
Jeannette T
JT
Jackson
Susan
S
Nyante
Sarah
S
Livasy
Chad
C
Carey
Lisa
L
Earp
H Shelton
HS
Perou
Charles M
CM
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