Estrogen receptors in breast cancer. Association with epidemiologic risk factors.

This study examined the factors influencing estrogen receptor protein levels in a population-based group of 168 incident cases of breast cancer in Olmsted County, Minnesota. The medical histories of women with histologically confirmed breast cancer and measured estrogen receptor levels in the period from November 1977 through December 1982 were reviewed. Statistically significant positive univariate associations were found between tumor estrogen receptor protein level and age, postmenopausal status, nulliparity, late age at first birth, cholelithiasis and educational level. No association was found between tumor estrogen receptor level and other breast cancer risk factors. After adjustment for age, there was no association between the above factors and estrogen receptor protein level. On multivariate analysis, age remained a statistically significant predictor of a higher estrogen receptor protein level. These findings in a population-based group of women with breast cancer are similar to previous reports of hospital-based breast cancer patients.