Optimal systemic therapy for premenopausal women with hormone receptor-positive breast cancer

Although systemic therapy is one of the cornerstones of therapy for premenopausal women with early stage breast cancer, there remain many unknowns regarding its optimal use. By accident of clinical trial design, much clinical investigation in premenopausal women has focused on chemotherapy. More recently the value of endocrine therapy (tamoxifen and ovarian suppression/ablation via surgery, LHRH agonists, or chemotherapy-induced menopause) has become apparent, and some form of endocrine therapy is viewed as standard for virtually all premenopausal women with early stage invasive breast cancer that expresses estrogen and/or progesterone receptor. Critical open questions include type and duration of endocrine therapy and the development of prognostic/predictive markers to help identify patients who are likely to benefit from chemotherapy in addition to endocrine therapy. For some years, five years of tamoxifen has been viewed as the standard endocrine therapy for premenopausal hormone-responsive breast cancer, although the ATLAS trial suggests that an additional five years of tamoxifen can be considered. The MA17 trial also suggests that an additional five years of an aromatase inhibitor can be considered for women who become postmenopausal during tamoxifen therapy. Information about the value of ovarian suppression continues to emerge, most recently with the demonstration of excellent outcome with goserelin plus tamoxifen in the ABCSG12 trial. The SOFT and TEXT trials, whose accrual is now complete, should help to define optimal endocrine therapy. In addition, use of the 21-gene recurrence score assay may help to delineate the additional value of chemotherapy for patients with node-negative breast cancer, and its utility in the setting of women with 1-3 positive lymph nodes is under study in the RxPONDER trial. Nonetheless, the need for other predictive biomarkers to select appropriate therapy remains real. Finally, attention to long term benefits and side effects of therapy will continue to be vital for these young women.