ESR1 and breast cancer: This phase 3, randomized, double-blind, placebo-controlled trial explored the use of ctDNA to identify patients with ESR1 mutations (ESR1m) after ≥6 months of front-line treatment for hormone-receptor positive (HR+)/HER2-negative advanced breast cancer to determine the benefit of switching from an aromatase inhibitor (AI) to the next-generation oral selective estrogen receptor degrader (SERD) and complete ER antagonist camizestrant at the time of “molecular progression” prior to disease progression.27