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Original Article
January 1, 2005

Risk Factors for Estrogen Receptor–Positive Breast Cancer

Author Affiliations

Author Affiliations: Departments of Surgery (Dr Hwang) and Epidemiology and Biostatistics (Drs Shiboski and Wrensch and Ms Chew), University of California, San Francisco; Marin Community Clinic, San Rafael, Calif (Dr Farren); and Buck Institute for Age Research, Novato, Calif (Dr Benz).

Arch Surg. 2005;140(1):58-62. doi:10.1001/archsurg.140.1.58

Hypothesis  Some risk factors associated with breast cancer may be more predictive of estrogen receptor (ER)− positive than ER-negative tumors.

Design  Survey of patients enrolled in a study of breast cancer risk factors.

Setting  Community population in a northern California county.

Patients  A total of 234 individuals diagnosed as having breast cancer between July 1, 1997, and June 30, 1999, reporting Marin County, California, residence and participating in a questionnaire regarding exposure to breast cancer risk factors.

Main Outcome Measure  Diagnosis of ER-positive vs ER-negative breast cancer.

Results  Comparison between ER-positive and ER-negative cases showed several factors predictive of ER-positive tumors. In a multivariate model, years of hormone therapy use remained the most significant predictor of ER-positive disease.

Conclusions  Patients diagnosed as having ER-positive breast cancer were more likely to have undergone hormone therapy. The excess of ER-positive breast cancers reported in Marin County could, therefore, in part, be related to hormone therapy.