Analysis of Circulating Tumor DNA to Monitor Metastatic Breast Cancer

Breast cancer is the most common cancer and the leading cause of cancer-related death in women worldwide.1 Metastatic breast cancer remains an incurable disease but is treatable by means of serial administration of endocrine, cytotoxic, or biologic therapies. The monitoring of treatment response is essential to avoid continuing ineffective therapies, to prevent unnecessary side effects, and to determine the benefit of new therapeutics. Treatment response is generally assessed with the use of serial imaging, but radiographic measurements often fail to detect changes in tumor burden. Therefore, there is an urgent need for biomarkers that measure tumor burden with high sensitivity . . .