title: Breast cancer risk factors defined by estrogen and progesterone receptor status: the multiethnic cohort study.
abstract: Prospective data on ethnic differences in hormone receptor-defined subtypes of breast cancer and their risk factor profiles are scarce. The authors examined the joint distributions of estrogen receptor (ER) and progesterone receptor (PR) status across 5 ethnic groups and the associations of established risk factors with ER/PR status in the Multiethnic Cohort Study (Hawaii and Los Angeles, California). During an average of 10.4 years of follow-up of 84,427 women between 1993-1996 and 2004/2005, 2,543 breast cancer cases with data on ER/PR status were identified: 1,672 estrogen receptor-positive (ER+)/progesterone receptor-positive (PR+); 303 ER+/progesterone receptor-negative (PR-); 77 estrogen receptor-negative (ER-)/PR+; and 491 ER-/PR-. ER/PR status varied significantly across racial/ethnic groups even within the same tumor stage (for localized tumors, P < 0.0001; for advanced tumors, P = 0.01). The highest fraction of ER-/PR- tumors was observed in African Americans (31%), followed by Latinas (25%), Whites (18%), Japanese (14%), and Native Hawaiians (14%). Associations differed between ER+/PR+ and ER-/PR- cases for postmenopausal obesity (P = 0.02), age at menarche (P = 0.05), age at first birth (P = 0.04), and postmenopausal hormone use (P < 0.0001). African Americans are more likely to be diagnosed with ER-/PR- tumors independently of stage at diagnosis, and there are disparate risk factor profiles across the ER/PR subtypes of breast cancer.
authors.affiliation: Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA. vsetiawa@usc.edu
authors.forename: Veronica Wendy
authors.initials: VW
authors.lastname: Setiawan
authors.forename: Kristine R
authors.initials: KR
authors.lastname: Monroe
authors.forename: Lynne R
authors.initials: LR
authors.lastname: Wilkens
authors.forename: Laurence N
authors.initials: LN
authors.lastname: Kolonel
authors.forename: Malcolm C
authors.initials: MC
authors.lastname: Pike
authors.forename: Brian E
authors.initials: BE
authors.lastname: Henderson