FDA approves Guardant360 CDx to catch ESR1 mutations before scans show progression

FDA approved Guardant360 CDx on September 4 as the companion diagnostic for AstraZeneca's Etcamah (camizestrant) in HR-positive, HER2-negative advanced or metastatic breast cancer. The test finds ESR1 mutations in circulating tumor DNA before radiographic progression. Patients are tested every three months while on an aromatase inhibitor and a CDK4/6 inhibitor.

SERENA-6 supported the label. Switching therapy on the blood result rather than the scan cut the risk of progression or death by 56% and raised median progression free survival from 9.2 months to 16.0 months. Guardant also reported a 47% reduction in the risk of quality of life deterioration.

This is the 29th companion diagnostic indication for Guardant360 and the first FDA approved liquid biopsy for serial monitoring in breast cancer. The regulatory precedent travels further than the oncology. FDA accepted a molecular event, not an imaging event, as the trigger for a treatment decision, which is the argument every monitoring device company has been trying to make.

Questions & Answers

What did the FDA approve Guardant360 CDx for in September 2026?

On September 4, 2026 the FDA approved Guardant Health's Guardant360 CDx as a companion diagnostic to identify ESR1 mutations in patients with HR-positive, HER2-negative advanced or metastatic breast cancer who may benefit from AstraZeneca's Etcamah (camizestrant).

What were the SERENA-6 results behind the Guardant360 CDx approval?

In SERENA-6, switching treatment on an ESR1 mutation detected by Guardant360 CDx cut the risk of progression or death by 56% and raised median progression free survival from 9.2 months to 16.0 months.

How often is Guardant360 CDx used under the camizestrant label?

The label calls for testing every three months during aromatase inhibitor and CDK4/6 inhibitor therapy, so an emerging ESR1 mutation is caught before radiographic progression.

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