Metastatic breast cancer is incurable, yet highly treatable with endocrine, HER2 directed and chemotherapies improving survival for many patients. Successful treatment depends on the ability to monitor disease burden and response to therapies. Recently, a proof of principle study has shown that plasma tumor DNA (ptDNA) can be used as a reliable breast cancer biomarker in metastatic disease, due to its sensitivity and wide dynamic range. ptDNA more accurately reflects changes in response to therapies, and absolute levels of ptDNA demonstrate prognostic significance. Thus, ptDNA as a liquid biopsy shows great promise in the clinical management of metastatic breast cancer though further technical challenges and larger confirmatory studies are needed.
Keywords: Plasma tumor DNA (ptDNA); circulating tumor DNA (ctDNA); metastatic breast cancer; plasma biomarker.