Abstract PL2: Plenary Lecture 2: Premenopausal ER+ Breast Cancer: Past, Present, and Future

Abstract

Abstract Adjuvant endocrine therapy for premenopausal ER+breast cancer had a relatively challenging initial pathway. The earliest trials testing adjuvant ovarian ablation in premenopausal breast cancer were hampered by the lack of ability to test for the relevant target, namely the estrogen receptor (ER). Therefore, trials testing adjuvant ovarian ablation and subsequently ovarian suppression with gonadotropin releasing hormone agonists (GnRHa) were diluted by the inclusion of women with estrogen receptor negative tumors. The subsequent demonstration of the effectiveness of adjuvant chemotherapy, initially with the CMF regimen, diverted some attention away from adjuvant endocrine therapy in premenopausal women, notwithstanding the fact that CMF, initially given for 12 months, resulted in permanent ovarian function suppression in many premenopausal women. Use of adjuvant CMF made it even more challenging to discern the added value of ovarian ablation or suppression. Oral adjuvant endocrine therapy with the selective estrogen receptor modulator tamoxifen became recommended for postmenopausal women, subsequently refined to only those with ER+ breast cancer, but the value of tamoxifen in premenopausal women was initially considered uncertain. Eventually, 5 years of adjuvant tamoxifen became a standard recommendation for premenopausal ER+ early breast cancer, although it took some time for evidence to emerge on the value of adding tamoxifen in women who received chemotherapy. The value of extending adjuvant endocrine therapy beyond 5 years was subsequently studied. More recent randomized premenopausal adjuvant endocrine therapy trials have focused of delineating the value of ovarian function suppression (OFS) added to tamoxifen or to an aromatase inhibitor. There are now a range of options for adjuvant endocrine therapy for premenopausal ER+ breast cancer, and identifying the clinical-pathologic features most appropriate for intensification of adjuvant endocrine therapy can assist with optimizing recommendations for an individual patient. Citation Format: Carlos Arteaga, Prudence Francis. Plenary Lecture 2: Premenopausal ER+ Breast Cancer: Past, Present, and Future [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PL2.