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William J. Gradishar, MD, FACP, FASCO
William J. Gradishar, MD, FACP, FASCO
Posted: Friday, July 14, 2023
A post hoc subgroup analysis of the phase III EMERALD trial revealed that the duration of prior CDK4/6 inhibition may predict the efficacy of elacestrant in patients with ESR1-mutated estrogen receptor–positive, HER2-negative advanced or metastatic breast cancer. However, according to Virginia G. Kaklamani, MD, of UT Health San Antonio, and colleagues, data are limited regarding the clinical activity of this selective estrogen receptor degrader in those with ESR1 mutation–undetectable disease. These results, which were presented during the 2023 American Society for Clinical Oncology (ASCO) Annual Meeting (Abstract 1070), demonstrated a progression-free survival benefit in a population of such patients who experienced disease progression within 6 months of initiating CDK4/6 inhibition plus endocrine therapy.
“While caution needs to be exerted given small numbers, the results highlight the potential role of elacestrant in ESR1 wild-type tumors, and more research is warranted,” the investigators concluded.
A total of 478 patients who were previously administered one to two lines of endocrine therapy, CDK4/6 inhibition, and up to one line of chemotherapy were randomly assigned in a 1:1 ratio to receive oral elacestrant or standard-of-care endocrine monotherapy with the investigator’s choice of an aromatase inhibitor or fulvestrant. Of this total study population, 250 did not have a detectable ESR1 mutation.
The median durations of progression-free survival were 5.3, 1.9, and 2.3 months with elacestrant and 1.9, 2.0, and 2.0 months with the standard of care, respectively, in 41 ESR1 mutation–undetectable patients who experienced disease progression after less than 6 months (hazard ratio [HR] = 0.518), at least 6 months (HR = 0.911), and at least 12 months (HR = 0.886) of CDK4/6 inhibition plus endocrine therapy. In this population, the median time to initiation of subsequent chemotherapy was 137.7 days with elacestrant versus 75.5 days with the standard of care. The safety results were found to be consistent with previous reports.
Disclosure: For full disclosures of the study authors, visit coi.asco.org.
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