Incidence and predictors of ovarian function recovery (OFR) in exemestane patients with breast cancer (BC) with chemotherapy-induced amenorrhea (CIA) using two estradiol assays.

521 Background: Aromatase inhibitors (AIs) may promote OFR in patients with CIA. True incidence of OFR is unknown partly because estradiol (E2) assays used in the clinical setting lacking sensitivity. We studied incidence and predictors of OFR measuring E2 by a clinical assay (direct) or by a highly sensitive (indirect) immunoassay, together with other markers of ovarian reserve. Methods: Prospective exploratory study in ER positive BC patients, who had CIA lasting at least two years and postmenopausal E2 levels, while on tamoxifen. Patients received exemestane and underwent assessments of E2 (indirect and direct assay), FSH, antimullerian hormone (AMH), and antral follicule count (AFC) at baseline and at month 1, 3 and 6. We considered OFR if: resumption of menses, or developed (i) both E2 levels inconsistent with postmenopausal women on AI (indirect: >8 pmol/L; direct >165 pmol/L) and FSH ( 55 pmol/L; direct >220 pmol/L). Results:...