Abstract
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 the BRAFV600E mutations (cfBRAFV600E) in plasma samples from 57 patients with papillary thyroid cancer (PTC) with somatic BRAFV600E mutation-positive primary tumors using microfluidic digital PCR, and co-amplification at lower denaturation temperature (COLD) PCR. Mutant cfBRAFV600E alleles were detected in 24/57 (42.1%) of the examined patients. The presence of cfBRAFV600E was 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, cfBRAFV600E was detected in 4/19 (21.0%), 8/22 (36.3%) and 12/16 (75.0%) of cases, respectively. Patients with detectable cfBRAFV600E were 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 of BRAFV600E in 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.