title: The relationship between menstrual factors and breast cancer according to estrogen receptor status of tumor: a case-control study in African-American women.
abstract: BACKGROUND
  Exposure to estrogen is a risk factor for breast cancer. Since estrogen executes its effect through estrogen receptors (ERs), the relationship between menstrual factors, which are estrogen-related, and breast cancer may be different depending upon ER status of tumors. This case-control study aimed to examine such a relationship according to ER status of breast cancer in African-American women.
  
  
  METHODS
  Cases were 304 African-American patients pathologically diagnosed with breast cancer during 1995-1998, who were 20-64 years old and lived in 3 Tennessee counties. Controls were 305 African-American women without breast cancer, selected through random-digit dialing and frequency matched to cases by age and county. Information on menstrual factors (age at menarche, age at menopause, time from menarche to menstrual regularity, cycle length, and length of flow) and other risk factors were collected through telephone interviews. Estrogen receptor status of tumor samples was defined based on immunohistochemical measurement. Logistic regression analysis was used to calculate odds ratios and 95% confidence interval (CI).
  
  
  RESULTS
  Compared to women with an average cycle length less than 28 days, the risks of breast cancer for those with longer length were 0.62 (95% CI, 0.36-1.06) and 0.56 (95% CI, 0.32-1.00) for ER-positive and ER-negative tumors, respectively. The corresponding odds ratio (OR) estimates were 0.42 (95% CI, 0.20-0.86) and 0.38 (95% CI, 0.16-0.90) for postmenopausal women. Other menstrual factors were not significantly associated with breast cancer for either ER status.
  
  
  CONCLUSIONS
  Our results did not show a different menstrual factor/breast cancer relationship in terms of ER status in African-American women, although there might be an association between menstrual cycle length and the disease.
authors.affiliation: Department of Health Evaluation Sciences, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania 17033-0855, USA. kzhu@hes.hmc.psu.edu
authors.forename: Kangmin
authors.initials: K
authors.lastname: Zhu
authors.forename: Jessica
authors.initials: J
authors.lastname: Beiler
authors.forename: Sandra
authors.initials: S
authors.lastname: Hunter
authors.forename: Kathleen
authors.initials: K
authors.lastname: Payne-Wilks
authors.forename: Chanel L
authors.initials: CL
authors.lastname: Roland
authors.forename: Digna S
authors.initials: DS
authors.lastname: Forbes
authors.forename: Vernon M
authors.initials: VM
authors.lastname: Chinchilli
authors.forename: Louis J
authors.initials: LJ
authors.lastname: Bernard
authors.forename: Kathryn H
authors.initials: KH
authors.lastname: Jacobsen
authors.forename: Robert S
authors.initials: RS
authors.lastname: Levine
mesh_terms: D000328:Adult; D001741:Black or African American; D001943:Breast Neoplasms / Q000208:ethnology / Q000378:metabolism* / Q000503:physiopathology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008597:Menstrual Cycle / Q000208:ethnology; D008875:Middle Aged; D011960:Receptors, Estrogen / Q000378:metabolism*; D012307:Risk Factors; D013714:Tennessee
chemical_list: D011960:Receptors, Estrogen