For the project “Characterization of Treatment Response in Thyroid Cancer by cfDNA.” This project seeks to explore if “liquid biopsy: can be used as a tool to gain insight into the tumor biology of thyroid cancer, simply from a vial of blood, and ultimately translate these findings into new targeted therapies. The project aims to develop novel biomarkers that allow for early detection of resistance to the newer targeted therapies for thyroid cancer that is refractory to radioactive iodine. The research will determine the tumor fraction, copy number alterations and somatic mutations from tumor-derived cfDNA, and compare with the results from tissue biopsy.