With multiple FDA-approved oral SERDs available, clinical decision-making is heavily influenced by their distinct side effect profiles. Elacestrant predominantly causes nausea, while iminoralestrant causes diarrhea. This distinction is a primary factor in tailoring treatment to individual patients.
ESR1 mutations are rarely found in primary tumors but develop in metastatic settings under pressure from aromatase inhibitors, conferring resistance. This evolution necessitates serial, plasma-based genotyping upon each disease progression to identify these actionable mutations as they emerge.
Post-approval, real-world analyses have validated the efficacy of elacestrant seen in the pivotal EMERALD trial. This confirmation shows that the clinically meaningful progression-free survival of 6-8 months is achievable in routine clinical practice, boosting clinician confidence.
A simple clinical biomarker—having received a prior CDK4/6 inhibitor for over 12 months—identifies patients likely to achieve significant progression-free survival (nearly nine months) with single-agent elacestrant. This allows clinicians to select patients for monotherapy without complex genomic profiling.
The success of oral SERD clinical trials hinges on study design. Trials like AMIRA-3 and Axilera failed in their overall populations but showed benefit in ESR1-mutant subgroups. EMERALD succeeded by making this subgroup a co-primary endpoint, proving the importance of targeting the right population from the outset.
The SERINA-6 trial supports a paradigm shift: proactively screening for ESR1 mutations via blood test and switching to camisestrant upon detection, even without radiological progression. This early switch based on molecular signals nearly doubled median progression-free survival from 9 to 16 months.