Why is fulvestrant not used for pre-menopausal patients?

High estrogens. Premenopausal women produce large quantities of estrogens which feed the Cancer. So the treatments that work best for them are those that remove the source of estrogens or block its effects on the tumor. Fulvestant does not work that way, so it is relatively less effective in premenopausal patients.

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Why is fulvestrant not used with pre-menopausal patient?

Competition. Circulating Estradiol competes with for the estrogen receptor in premenopausal women. Estradiol surges during ovulation to fairly high levels where in postmenopause, Estradiol is made from converting androgens/adrenal hormones (like dhea) in peripheral fat. Levels are not as high so competition for the receptor is less. Read more...