Challenges in Treating Premenopausal Women with Endocrine-Sensitive Breast Cancer.

For the hundreds of thousands of premenopausal women who are diagnosed annually with endocrine-sensitive breast cancer, treatment strategies are complex. For many, chemotherapy may not be necessary, and endocrine therapy decision making is paramount. Options for adjuvant endocrine regimens include tamoxifen for 5 years, tamoxifen for 10 years, ovarian function suppression (OFS) plus tamoxifen for 5 years, and OFS plus an aromatase inhibitor for 5 years. There are modest differences in efficacy between these regimens, with a benefit from OFS most obvious among patients with higher-risk disease; therefore, choosing which should be used for a given patient requires consideration of expected toxicities and patient preferences. An aromatase inhibitor cannot be safely prescribed without OFS in this setting. Additional research is needed to determine whether genomic tests such as Prosigna and Endopredict can help with decision making about optimal duration of endocrine therapy for premenopausal patients. Endocrine therapy side effects can include hot flashes, sexual dysfunction, osteoporosis, and infertility, all of which may impair quality of life and can encourage nonadherence with treatment. Ovarian function suppression worsens menopausal side effects. Hot flashes tend to be worse with tamoxifen/OFS, whereas sexual dysfunction and osteoporosis tend to be worse with aromatase inhibitors/OFS. Pregnancy is safe after endocrine therapy, and some survivors can conceive naturally. Still, embryo or oocyte cryopreservation should be considered at the time of diagnosis for patients with endocrine-sensitive disease who desire future childbearing, particularly if they will undergo chemotherapy.