Estrogen and progesterone receptor concentrations and prevalence of tumor hormonal phenotypes in older breast cancer patients.

We examined the concentrations of estrogen (ER) and progesterone receptors (PR) and the distribution of tumor phenotypes as a function of age in breast cancer patients. ER and PR concentrations were determined in tissue biopsies from 1739 patients with primary breast cancer, using ligand binding assays. Tumors were classified as estrogen receptor positive (ER+) or negative (ER-) and progesterone receptor positive (PR+) or negative (PR-) based on the presence or absence of receptor binding activity. Tumors were stratified into four phenotypes: ER+PR+; ER+PR-; ER-PR+; and ER-PR-. Significant positive associations were found between ER concentration and age (p = 0.0001) and between PR concentration and age (p = 0.0002). The median ER concentrations were statistically different by age groups, with the greatest levels in older versus younger patients. The prevalence of ER+PR+ tumor phenotype increased with age. In contrast, the prevalence of ER-PR- and ER-PR+ tumor phenotypes decreased with age. The median PR-to-ER ratio decreased with age (p = 0.0001), and this trend was attributed to increased ER concentration with age. The prevalence of ER-PR- and ER-PR+ tumor phenotypes is greater in younger patients suggesting that hormonal regulation of ER gene expression may be responsible for the observed age disparity of tumor phenotypes in breast cancer.