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.
Hargis
Jeffrey B
JB
Kentuckiana Cancer Institute PLLC, Louisville, Kentucky 40202, USA.
Nakajima
Steven T
ST
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