Hormone receptors in endometrial cancer.

Similarities between endometrial and mammary tissue as targets for ovarian hormones indicate that measurements of estradiol and progesterone receptor (RE and RP) levels may be as useful in endometrial cancer as they are in breast cancer for the prediction of responses to treatment with steroids and antiestrogens. Receptor levels cannot be inferred from the degree of differentiation of the endometrial tumors, although RP values are lower in poorly differentiated adenocarcinoma. Current studies aim to relate RP levels to objective remissions of metastases after progestin therapy, and attempts are being made to increase RP with tamoxifen before treatment with progestins or assaying for RP. In vitro studies aim to elucidate fundamental problems related to the action of steroids on the tumors, e.g., mechanism by which receptors mediate the effects of pharmacologic doses of drugs, factors that regulate receptor levels, and homogeneity in the distribution of receptors in tumor cell populations.