(HealthDay News) — Use of tamoxifen and age at treatment for breast cancer predict chemotherapy-induced amenorrhea among premenopausal women, according to research published online Aug. 26 in the Journal of Clinical Oncology.

Adriana Valentini, M.D., from the University of Toronto, and colleagues conducted a multicenter survey of 1,954 young women with a BRCA1 or BRCA2 mutation who were treated for breast cancer; premenopausal women diagnosed with invasive breast cancer between 26 and 47 years of age were included. Chemotherapy-induced amenorrhea was defined as when the patient experienced two or more years of amenorrhea, beginning within 2 years of initiating chemotherapy and with no resumption of menses.

The researchers found that, of the 1,426 women who received chemotherapy, 35% experienced long-term amenorrhea, while 5.3% of the 528 women who did not receive chemotherapy developed long-term amenorrhea. The probability of chemotherapy-induced amenorrhea increased with age: 7.2% for women diagnosed before age 30, 33% for women aged 31 to 44, and 79% for women diagnosed after age 45 (P trend < 0.001). Compared to women who did not receive tamoxifen, the probability of induced amenorrhea was higher for those who did (52% versus 29%; P < 0.001).

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“Age at treatment and use of tamoxifen are important predictors of chemotherapy-induced amenorrhea in women who carry a BRCA1 or BRCA2 mutation,” the authors write. “The risk of induced long-term amenorrhea does not seem to be greater among mutation carriers than among women who do not carry a mutation.”