Retrospective analysis of real-world elacestrant use in two large Austrian cancer centers

Background: Elacestrant is an oral selective estrogen receptor degrader (SERD) approved for the treatment of hormone receptor–positive (HR-positive), human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC) following progression on endocrine therapy and CDK4/6 inhibitors. While randomized trial data from the EMERALD study demonstrated its clinical benefit, real-world evidence remains limited. Methods: We conducted a retrospective chart review of patients with HR-positive/HER2-negative MBC treated with elacestrant at two large cancer centers in Vienna, Austria. Clinical outcomes and safety were evaluated in routine clinical practice by experienced oncologists. Results: Elacestrant demonstrated clinically meaningful efficacy in a heavily pretreated patient population of 30 patients with estrogen receptor 1 (ESR1) mutations. Median age was 65 years and the cohort was predominantly postmenopausal (86.7%). Before initiation of elacestrant, patients had received a median of two lines of endocrine therapy and one line of chemotherapy. Co-mutations of ESR1/PIK3CA were present in 33.3% of patients. Median progression-free survival (PFS) was 3.6 months (95% CI 2.96 – 4.24) and median overall survival (OS) was 20.2 months (95% CI 5.04 – 35.36). Adverse events of any grade were found in 46.7% of patients. Within our cohort, a low rate of dose reductions (3.3%) was found. Subsequent therapies after elacestrant mainly consisted of antibody-drug conjugates (36.7% of patients) and chemotherapy (26.7%). Conclusion: In this real-world cohort, elacestrant showed effectiveness and tolerability similar to data observed in the EMERALD trial. Larger prospective real-world analyses are warranted to further validate these findings and define optimal patient selection.