Retrospective Analysis of Real-World Elacestrant Use in Two Large Austrian Cancer Centers

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.

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.

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 was 20.2 months (95% CI 5.04-35.36). In univariate analyses, de novo metastatic disease and the presence of a single ESR1-mutated exon were associated with longer PFS, whereas the ESR1 E380Q mutation was associated with shorter PFS. Adverse events of any grade occured 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%).

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.