Detection of BRAFV600E in Liquid Biopsy from Patients with Papillary Thyroid Cancer Is Associated with Tumor Aggressiveness and Response to Therapy

The detection of rare mutational targets in plasma (liquid biopsy) has emerged as a promising tool for the assessment of patients with cancer. We determined the presence of cell-free DNA containing theBRAFV600Emutations (cfBRAFV600E) in plasma samples from 57 patients with papillary thyroid cancer (PTC) with somaticBRAFV600Emutation-positive primary tumors using microfluidic digital PCR, and co-amplification at lower denaturation temperature (COLD) PCR. Mutant cfBRAFV600Ealleles were detected in 24/57 (42.1%) of the examined patients. The presence of cfBRAFV600Ewas significantly associated with tumor size (p= 0.03), multifocal patterns of growth (p= 0.03), the presence of extrathyroidal gross extension (p= 0.02) and the presence of pulmonary micrometastases (p= 0.04). In patients with low-, intermediate- and high-risk PTCs, cfBRAFV600Ewas detected in 4/19 (21.0%), 8/22 (36.3%) and 12/16 (75.0%) of cases, respectively. Patients with detectablecfBRAFV600Ewere characterized by a 4.68 times higher likelihood of non-excellent response to therapy, as compared to patients without detectable cfBRAFV600E (OR (odds ratios), 4.68; 95% CI (confidence intervals)) 1.26-17.32;p= 0.02). In summary, the combination of digital polymerase chain reaction (dPCR) with COLD-PCR enables the detection ofBRAFV600Ein the liquid biopsy from patients with PTCs and could prove useful for the identification of patients with PTC at an increased risk for a structurally or biochemically incomplete or indeterminate response to treatment.