Association Between (18)F-FDG Avidity and the BRAF Mutation in Papillary Thyroid Carcinoma.

Abstract

The BRAF mutation, a potential prognostic factor in papillary thyroid carcinoma (PTC), is associated with a high expression of the glucose transporter gene. We investigated which clinicopathologic factors, including BRAF mutation status, influence (18)F-fluoro-2-deoxyglucose ((18)F-FDG) avidity. We retrospectively reviewed 55 patients who underwent BRAF analysis from biopsy-confirmed PTC and (18)F-FDG positron emission tomography/computed tomography within 6months before undergoing thyroid surgery from September 2008 to August 2014. Tumors were considered to be (18)F-FDG avid if the uptake was greater than that of the liver. (18)F-FDG uptake of PTCs was also analyzed semiquantitatively using SUVmax. The association between (18)F-FDG avidity and clinicopathologic variables (age, tumor size, perithyroidal extension, cervical lymph node status, and BRAF mutation status) was investigated. Twenty-nine (52.7%) of 55 patients had (18)F-FDG-avid PTCs. PTCs with the BRAF mutation showed higher (18)F-FDG avidity (24/38, 63.2%) than those without (5/17, 29.4%). The BRAF mutation (p = 0.025) and tumor size (p = 0.003) were significantly associated with (18)F-FDG avidity in univariate analysis, and the BRAF mutation status remained significant after adjusting for tumor size in multivariate analysis (p = 0.015). In the subgroup of tumor size ≥ 1cm, the BRAF mutation was the only factor significantly associated with (18)F-FDG avidity (p = 0.021). The mean SUVmax of PTCs with the BRAF mutation was significantly higher than that of those without (4.89 ± 6.12 vs. 1.96 ± 1.10, p = 0.039). The BRAF mutation must be one of the most important factors influencing (18)F-FDG avidity in PTCs, especially in those with a tumor size ≥ 1cm.