Correlation of BRAFV600E Mutation and Glucose Metabolism in Thyroid Cancer Patients: An 18F-FDG PET Study

There is significant interest in a better understanding of the genetic underpinnings of the increased glucose metabolic rates of cancer cells. Thyroid cancer demonstrates a broad variability of 18F-FDG uptake as well as several well-characterized oncogenic mutations. In this study, we evaluated the differences in glucose metabolism of the BRAFV600E mutation versus BRAF wild-type (BRAF-WT) in patients with metastatic differentiated thyroid cancer (DTC) and poorly differentiated thyroid cancer (PDTC). Methods: Forty-eight DTC and 34 PDTC patients who underwent 18F-FDG PET/CT for tumor staging were identified from a database search. All patients were tested for the BRAFV600E mutation and assigned to 1 of 2 groups: BRAFV600E mutated and BRAF-WT. 18F-FDG uptake of tumor tissue was quantified by maximum standardized uptake value (SUVmax) of the hottest malignant lesion in 6 prespecified body regions (thyroid bed, lymph nodes, lung, bone, soft tissue, and other). When there were multiple lesions in 1 of the prespecified body regions, only the 1 with the highest 18F-FDG uptake was analyzed. Results: In the DTC cohort, 24 tumors harbored a BRAFV600E mutation, whereas 24 tumors were BRAF-WT. 18F-FDG uptake of BRAFV600E-positive lesions (median SUVmax, 6.3; n = 53) was significantly higher than that of BRAF-WT lesions (n = 39; median SUVmax, 4.7; P = 0.019). In the PDTC group, only 5 tumors were BRAFV600E-positive, and their 18F-FDG uptake was not significantly different from the BRAF-WT tumors. There was also no significant difference between the SUVmax of all DTCs and PDTCs, regardless of BRAF mutational status (P = 0.90). Conclusion: These data suggest that BRAFV600E-mutated DTCs are significantly more 18F-FDG–avid than BRAF-WT tumors. The effect of BRAFV600E on tumor glucose metabolism in PDTC needs further study in larger groups of patients.