The FDA approved camizestrant for ESR1-mutated HR+/HER2– advanced breast cancer, enabling earlier ctDNA-guided switching to the oral SERD in patients who develop ESR1 resistance while on aromatase inhibition plus a CDK4/6 inhibitor. The approval is tied to SERENA-6 data showing an improvement in progression-free survival and delayed deterioration in quality of life versus continuing aromatase inhibitor therapy. Camizestrant’s label positions ctDNA monitoring as a mechanism to intervene at molecular progression rather than waiting for clinical decline. Dana-Farber’s Erica L. Mayer, who discussed the approval in an interview, framed the decision as opening access to a regimen designed to target ESR1 resistance sooner in the treatment course. The development also reinforces a broader regulatory shift toward integrating companion testing and liquid-biopsy endpoints into treatment sequencing—an area increasingly relevant for pharma seeking lifecycle differentiation in hormone receptor-positive disease.