Circulating tumor DNA (ctDNA) as a molecular monitoring tool in metastatic breast cancer (MBC).

11093 Background: MBC is an incurable disease with complex molecular features including somatic mutations that evolve in relation to genomic instability and selective treatment pressure. Circulating DNA fragments carrying tumor-specific sequence alterations (ctDNA) are found in blood and offer the possibility of longitudinal non-invasive molecular monitoring of the disease by detecting actionable mutations. Methods: This is a prospective evaluation of 18 patients with locally advanced or metastatic breast cancer who failed standard therapies and had plasma analyzed for ctDNA detection. Selection criteria: progression of disease after standard therapies, need to detect novel molecular abnormalities for possible therapeutic targeting, or confirmation of genomic abnormalities already demonstrated in tissue analysis. Guardant Health performed the plasma analysis; first ctDNA was isolated from plasma using a Qiagen circulating nucleic acid kit, then a panel of 54 gene mutations associated with solid tumors as ...