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

Purpose: 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 18F-fluoro-2-deoxyglucose (18F-FDG) avidity. Methods: We retrospectively reviewed 55 patients who underwent BRAF analysis from biopsy-confirmed PTC and 18F-FDG positron emission tomography/computed tomography within 6 months before undergoing thyroid surgery from September 2008 to August 2014. Tumors were considered to be 18F-FDG avid if the uptake was greater than that of the liver. 18F-FDG uptake of PTCs was also analyzed semiquantitatively using SUVmax. The association between 18F-FDG avidity and clinicopathologic variables (age, tumor size, perithyroidal extension, cervical lymph node status, and BRAF mutation status) was investigated. Results: Twenty-nine (52.7 %) of 55 patients had 18F-FDG-avid PTCs. PTCs with the BRAF mutation showed higher 18F-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 18F-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 ≥ 1 cm, the BRAF mutation was the only factor significantly associated with 18F-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). Conclusions: The BRAF mutation must be one of the most important factors influencing 18F-FDG avidity in PTCs, especially in those with a tumor size ≥ 1 cm. © 2015, Korean Society of Nuclear Medicine.