Adjuvant endocrine therapy choices in premenopausal patients with hormone receptor-positive early breast cancer: Insights from the prospective GIM23-POSTER study.

Most premenopausal patients with early breast cancer (eBC) are diagnosed with hormone receptor-positive disease and therefore candidate for adjuvant endocrine therapy (ET). The Gruppo Italiano Mammella (GIM) 23-POSTER (GIM23) is a multicenter, prospective, observational study conducted in 26 Italian institutions, aiming to evaluate ET choices for premenopausal patients affected by hormone receptor-positive eBC in a real-world setting. Here we report also the results in terms of type of ET prescribed according to the definition of high-risk patients by monarchE and NATALEE trials. Between October 2019 and June 2022, 600 premenopausal patients were included, with a median age of 46 years. Almost half (271, 45.2 %) of the patients had stage I disease, while 254 (42.3 %) and 60 (10.0 %) patients had stage II and III, respectively. Overall, 149 (25.1 %) patients received tamoxifen alone, 83 (14.0 %) tamoxifen with ovarian function suppression (OFS), while 361 (60.9 %) received aromatase inhibitor (AI) with OFS. Patients treated with AI and OFS had higher number of metastatic axillary nodes, higher grade and more often received chemotherapy (all p < 0.001). According to the inclusion criteria of the monarchE and NATALEE trials, 81 patients (15.6 %) were considered high-risk for the monarchE and received AI with OFS in 88.9 % of the cases, while 231 patients (44.4 %) were considered high-risk for the NATALEE trial and received AI with OFS in 74.5 % of cases. AI with OFS is the most prescribed adjuvant ET among premenopausal patients, especially in the presence of high-risk features. • GIM23 is a prospective study including premenopausal patients with early breast cancer. • Main objective is to assess the choices of adjuvant endocrine therapy. • Aromatase inhibitor with ovarian function suppression is the most prescribed strategy. • Less prescribed strategy is tamoxifen with ovarian function suppression. • Almost half of premenopausal patients could be candidate to adjuvant CDK4/6 inhibitors. [ABSTRACT FROM AUTHOR]