CHICAGO — Can spotting an emerging ESR1 mutation early and changing first-line drugs before progression improve outcomes in patients with hormone receptor (HR)–positive, human epidermal growth factor receptor 2–negative advanced breast cancer?

Interim findings from the SERENA-6 trial suggest that may be the case.

Patients who switched from a first-line aromatase inhibitor to camizestrant, an investigational next-generation oral selective estrogen-receptor degrader, at the first signs of an emerging ESR1 mutation demonstrated significantly improved progression-free survival compared with those who continued their initial regimen.

Notably, circulating tumor DNA (ctDNA) testing allowed investigators to identify ESR1 mutations, which emerge at the time of disease progression in abou

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