Women with a breast cancer responsive to estrogens often undergo adjuvant therapy to reduce circulating estrogen. This may be done with tamoxifen or an aromatase inhibitor. Serum levels of estradiol should be monitored in perimenopausal or postmenopausal women receiving estrogen suppression.
Aromatase inhibitors include:
(1) letrozole
(2) anastrozole
Estrogen to monitor: estradiol (E2)
Goal of therapy: serum estradiol concentrations below the level of quantitation
Rationale for monitoring: a small percentage of women will show initial estrogen suppression, only later to show increasing levels (aromatase inhibitor failure).
Method of analysis: LC/MS, since immunoassays may give false positive readings due to interferences.
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