Liquid Biopsy as a Method for Minimally Invasive Diagnosis of Thyroid Cancer

Thyroid cancer is the 9th most common cancer in the world. The five-year survival rate for this disease is over 98%. However, in some patients there are cases of rapidly progressive treatment-resistant cancer that cannot be differed from poor-invasive cancer by routine methods. Liquid biopsy could be one of the methods to solve this problem. This procedure consists in the analysis of tumor derivatives (in particular, circulating DNA) in body fluids. The analysis of hotspot mutations and patterns of epigenetic regulation, which are usual for neoplasms with a certain genotype, is used to identify the tumor component in the total mass of circulating DNA. The increase of circulating tumor DNA in the plasma is observed several months ahead of the characteristic signs at MR images of patients, and also surpasses conventional biomarkers such as calcitonin in medullary thyroid carcinoma. In addition, a possibility of minimally invasive determination of the tumor genotype by analyzing circulating DNA is important to select the optimal chemotherapy. This review discusses the current advances in the analysis of circulating tumor DNA in thyroid cancers such as papillary, follicular, medullary, and anaplastic carcinomas.