Can [18F]-fluorodeoxyglucose standardized uptake values of PET imaging predict pathologic extrathyroid invasion of thyroid papillary microcarcinomas?

Objective. To evaluate the hypothesis that the [F-18]-fluorodeoxyglucose (FDG) standardized uptake values (SUVs) of positron emission tomographic (PET) imaging can predict pathologic extrathyroid invasion of thyroid papillary microcarcinomas (TPMC). Design: Prospective clinical study. Method: From 2004 to 2005,44 consecutive patients with TPMC (<= 1 cm), confirmed by ultrasonography and aspiration cytology, had FDG PET scans performed. Among them, 66 tumor foci in 41 patients were confirmed to be of less than 1 cm in diameter by the final surgical pathology report. According to the microcarcinoma tumor focus, prediction of pathologic extrathyroid invasion, by clinical variables including sonographic findings and SUVs from PET imaging, was evaluated by the univariate and multivariate logistic regression analysis. Results: Univariate analysis showed that the tumor site attached to the thyroid capsule and the SUVs of PET imaging could predict pathologic extrathyroid invasion. However, the tumor site attached to thyroid capsule and an age older than 45 were significant predictors by multivariate analysis (P =.001 and P =.036). SUVs from PET imaging were only correlated with the size of tumor (P < 0.001). Conclusion: The SUVs from FDG PET imaging alone cannot predict the pathologic extrathyroid invasion in patients with TPMC. However, the ultrasonographic findings, such as tumor site, provide better information about the extrathyroid invasion of TPMC tumor foci.