Outcomes of elacestrant in patients with ER-positive, HER2-negative, ESR1-mutated metastatic breast cancer who received prior endocrine therapy and cyclin-dependent kinase inhibitor in a real-world setting.

BACKGROUND: Real-world data analyses show durable benefits with elacestrant, with or without prior treatment with cyclin-dependent kinase 4/6 inhibitor (CDK4/6i). This cohort focused on patients with ER-positive/HER2-negative estrogen receptor 1 (ESR1)-mutated metastatic breast cancer (mBC) treated with elacestrant after at least one line of endocrine therapy (ET) combined with CDK4/6i (N = 281). PATIENTS AND METHODS: Claims data from the Komodo Research Dataset linked with Foundation Medicine clinical-genomics data were used. Primary outcome was median time-to-next-treatment (mTTNT). RESULTS: In patients with ER-positive/HER2-negative ESR1-mutated mBC who received one to two prior lines of ET + CDK4/6i (n = 108), mTTNT with elacestrant was 8.2 months [95% confidence interval (CI) 6.0-12.2]. In patients who received one to two prior lines of ET + CDK4/6i for ≥12 months (n = 85), mTTNT was 9.0 months (95% CI 7.7-13.7), including an mTTNT of 12.2 months (95% CI 9.0-not reached) in those who received one prior line of ET (n = 31). In patients with liver and/or lung metastasis (n = 169), mTTNT was 6.9 months (95% CI 5.8-8.3), whereas it was 7.4 months (95% CI 5.6-12.9) in patients with brain metastasis (n = 68). In patients with coexisting ESR1- and phosphoinositide 3-kinase-pathway-mutated tumors (n = 115), mTTNT was 6.1 months (95% CI 5.0-8.1). CONCLUSIONS: Elacestrant showed durable benefits in patients with ER-positive/HER2-negative ESR1-mutated mBC previously exposed to at least one line of ET + CDK4/6i, reinforcing the role of elacestrant as a potential first-choice option for patients with endocrine-sensitive tumors.