ESTROGEN AND PROGESTERONE RECEPTORS IN THE ENDOMETRIUM OF POSTMENOPAUSAL BREAST-CANCER PATIENTS TREATED WITH TAMOXIFEN AND PROGESTOGENS

Postmenopausal breast cancer patients who were treated with tamoxifen and progestogens showed a uniform decidual reaction of the endometrium . It is well established that progestogens antagonize the estrogen eff ect on the endometrium by reducing its receptors in the endometrium. T o assess in vivo such a possible effect of progestogens on endometrium primarily exposed to tamoxifen, we analyzed estrogen and progesterone receptors (ER, PR) on endometrial specimens showing decidualization f rom nine postmenopausal breast cancer patients on tamoxifen and proges togen treatment and on endometrial polyps with areas of decidualizatio n from two other similar patients. ER was weakly detected in the endom etrial glands of four (36.4%) patients and in the endometrial stroma o f one (9.1%) patient. PR was detected in the endometrial gland of only one (9.1%) patient. No PR was detected in the endometrial stroma. The re was no correlation between the length of tamoxifen treatment, the t amoxifen dosage, or the length of progestogen treatment and the ER or PR content, although progestogens administered for more than 3 consecu tive months in all patients. This relatively very low ER and PR conten t may be attributed to the antagonistic effect of progestogens on the ''priming'' estrogen-like effect of tamoxifen on the endometrium. (C) 1997 Academic Press.