Resumption of menses with initiation of letrozole after five years of amenorrhea on tamoxifen: caution needed when using tamoxifen followed by aromatase inhibitors.
BACKGROUND
Randomized trials in postmenopausal women have shown a benefit to substituting aromatase inhibitors for tamoxifen or using them sequentially following a full course of tamoxifen. The aromatase inhibitor letrozole has also been utilized for ovarian induction in premenopausal women.


METHODS
A premenopausal woman with early stage breast cancer became amenorrheic with adjuvant chemotherapy, and remained so during 5 years of daily tamoxifen. After discontinuing tamoxifen, laboratory studies confirmed an apparent postmenopausal state. Menses resumed following a 2-week course of letrozole.


CONCLUSIONS
Aromatase inhibitors need to be used with caution in women who stop menstruating following adjuvant chemotherapy or tamoxifen.
Kentuckiana Cancer Institute PLLC, Louisville, Kentucky 40202, USA.
Jeffrey B
JB
Hargis
Steven T
ST
Nakajima
D000328:Adult; D000568:Amenorrhea / Q000139:chemically induced*; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use; D047072:Aromatase Inhibitors / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy*; D005260:Female; D006801:Humans; D000077289:Letrozole; D008598:Menstruation / Q000187:drug effects*; D009364:Neoplasm Recurrence, Local / Q000517:prevention & control*; D009570:Nitriles / Q000627:therapeutic use*; D017698:Postmenopause / Q000187:drug effects; D017697:Premenopause / Q000187:drug effects; D013629:Tamoxifen / Q000627:therapeutic use; D014230:Triazoles / Q000627:therapeutic use*
D018931:Antineoplastic Agents, Hormonal; D047072:Aromatase Inhibitors; D009570:Nitriles; D014230:Triazoles; D013629:Tamoxifen; D000077289:Letrozole