Circulating Tumor DNA Profiling From Breast Cancer Screening Through to Metastatic Disease

We were able detect ctDNA across the breast cancer spectrum, notably in MBC where variants in <i>ESR1</i>, <i>TP53</i>, and <i>PIK3CA</i> predicted poor overall survival. The assay could be used to monitor emergence of resistance mutations such as in <i>ESR1</i> that herald resistance to aromatase inhibitors to tailor adjuvant therapies. However, we suggest caution is needed when interpreting results from a single plasma sample as variants were also detected in a small proportion of HCs.