Guardant Health, Inc. has announced significant findings from the Phase III SERENA-6 trial, demonstrating the clinical effectiveness of the Guardant360® CDx test in guiding treatment for breast cancer. The study showed that using a circulating tumor DNA-guided approach, the Guardant360 CDx test can detect emerging resistance in 1st-line therapy before radiological disease progression in advanced breast cancer. Results indicated that AstraZeneca's camizestrant reduced the risk of disease progression or death by 56% in patients with advanced HR-positive breast cancer who had an emergent ESR1 tumor mutation. These findings, presented at the 2025 ASCO Annual Meeting and published in The New England Journal of Medicine, highlight a new paradigm in using liquid biopsy to inform timely treatment changes, potentially improving patient outcomes.