Relationship among estrogen receptors, proliferative activity and menopausal status in breast cancer.

Kinetic and estrogen receptor (ER) determinations were performed on 357 primary breast cancers. The proliferative activity of the cell population was determined by the autoradiographic technique and expressed as [3H]thymidine labeling index (LI): the ER status was assessed by the absorption charcoal technique. From the overall analysis of the relationship between proliferative activity and ER status, by using the median LI value as cutoff of low and high proliferating tumors, a correlation between ER + status and low proliferative activity and between ER- status and high proliferative activity was observed in 64% of the cases. Menopausal status proved to be an important determinant of kinetic and ER features. In fact, the proliferative activity was always higher in ER--tumors than in ER + tumors within the same menopausal group, and a decrease in proliferative activity was observed from premenopause to postmenopause within ER + and ER--tumors. The analysis of the relation between ER levels and proliferative activity in ER + tumors also evidenced three main ER/LI clusters significantly related to premenopause, paramenopause and postmenopause. A particular indication of nodal involvement was evidenced for a cluster of tumors with low ER levels and high LI from postmenopausal patients. The three different, previously proposed kinetic groups of potential relevance for prognostic and therapeutic purposes were confirmed and more precisely defined by considering not only premenopause and postmenopause but also paramenopause.