Camizestrant combination delayed progression in advanced breast cancer, study shows
AstraZeneca's camizestrant combination therapy showed a 55% delay in first disease progression and a 37% delay in second progression in patients with advanced HR-positive breast cancer, according to SERENA-6 trial results.
AstraZeneca has released updated results from its Phase III SERENA-6 trial, indicating that a combination therapy involving camizestrant significantly delayed disease progression in patients with advanced hormone receptor (HR)-positive, HER2-negative breast cancer carrying an ESR1 mutation.
The trial compared switching to a camizestrant combination (camizestrant plus a CDK4/6 inhibitor) versus continuing standard of care (an aromatase inhibitor plus a CDK4/6 inhibitor). The camizestrant combination reduced the risk of first disease progression or death by 55% and the risk of second progression or death by 37%, demonstrating a sustained benefit beyond initial treatment.
Exploratory analyses also revealed a substantial reduction in circulating tumor DNA (ctDNA) levels. Patients treated with the camizestrant combination achieved a median 99% reduction in total ctDNA by week 8, with 51% achieving complete ctDNA clearance. This contrasts with a median 55% increase in ctDNA and 1.9% clearance in the standard-of-care arm.
The findings, presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, support the use of camizestrant-based therapy early in the treatment course for patients with ESR1-mutated advanced breast cancer. While overall survival (OS) data showed a numerical trend favoring the camizestrant combination, final analysis is pending.