Detection of the BRAF Mutation in Circulating Free Nucleic Acids as a Biomarker of Thyroid Cancer: A Review

Background: Liquid biopsy is a method that could potentially improve the management of thyroid cancer (TC) by enabling the detection of circulating tumor DNA and RNA (ctDNA, ctRNA). The BRAF mutation appears to be the most representative example of a biomarker in liquid biopsy, as it is the most specific mutation for TC and a target for molecular therapeutics. The aim of this review is to summarize the available data on the detection of the BRAF mutation in liquid biopsy in patients with TC. Methods: A comprehensive analysis of the available literature on the detection of the BRAF mutation in liquid biopsy in TC was performed. Thirty-three papers meeting the inclusion criteria were selected after full-text evaluation. Results: Eleven papers discussed correlations between BRAF mutation and clinicopathological characteristics. Nine studies tested the utility of BRAF detection in the assessment of residual or recurrent disease. Seven studies investigated BRAF-mutated circulating tumor nucleic acids (ctNA) as a marker of response to targeted therapy. In seven studies the method did not detect the BRAF mutation. Conclusions: This review shows the potential of BRAF-mutated ctNA detection in monitoring disease progression, particularly in advanced TC. The diagnostic value of BRAF-mutated ctNA detection appears to be limited to advanced TC. The choice of the molecular method (quantitative PCR [qPCR], droplet digital polymerase chain reaction [ddPCR], and next-generation sequencing [NGS]) should be made based on the turnaround time, sensitivity of the test, and the clinical indications. Despite the promising outcomes of some studies, there is a need to verify these results on larger cohorts and to unify the molecular methods.