N Engl J Med
ESR1-mutated advanced breast cancer: Switching from aromatase inhibitors to camizestrant boosted progression-free survival
June 4, 2025
Switching to camizestrant, an investigational selective estrogen-receptor degrader and complete ER antagonist, once ESR1 mutations emerged during 1st-line therapy led to significantly longer progression-free survival vs. staying on an aromatase-inhibitor, in patients with ER(+), HER2(-) advanced breast cancer. The drug was not FDA-approved at the time of trial report.
- Study. The phase 3 SERENA-6 trial (NCT04964934) included 3,256 patients with ER(+), HER2(-) advanced breast cancer. All patients underwent at least 6 months of 1st-line therapy with an aromatase inhibitor plus a CDK4/6 inhibitor (abemaciclib, palbociclib, ribociclib). ESR1 was assayed in circulating tumor DNA every 2-3 months. The 315 ESR1(+) patients who didn’t have radiologic progression were randomized to switching from an aromatase inhibitor to camizestrant 75 mg once daily vs. staying on an aromatase inhibitor; both groups continued CDK4/6 inhibitors. Primary outcome: progression-free survival.
- Results. Interim analysis at a median of 12.6 months follow-up showed that median progression-free survival was 16.0 months with camizestrant vs. 9.2 months with aromatase-inhibitors. Median time to deterioration in patient-reported global health status and quality of life: 23.0 months with camizestrant vs. 6.4 months with aromatase inhibitors. Discontinuation frequency due to adverse events: 1.3% with camizestrant vs. 1.9% with aromatase inhibitors.
Source:
Bidard FC; SERENA-6 Study Group; et al. (2025, June 1). N Engl J Med. First-Line Camizestrant for Emerging ESR1-Mutated Advanced Breast Cancer. https://pubmed.ncbi.nlm.nih.gov/40454637/
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