Preoperative FDG PET/CT in papillary thyroid carcinoma for prediction of recurrence

Objectives It is not known if preoperative FDG PET/CT can predict recurrence in papillary thyroid carcinoma (PTC). We evaluated the potential of primary tumor FDG avidity for prediction of tumor recurrence in PTC patients.

Methods This retrospective study evaluated 412 PTC patients (M:F=72:340, age 47.2±12.2 years, range 17~84 years) who underwent FDG PET/CT prior to total thyroidectomy (n=352) or lobectomy (n=60) from 2007 to 2011. Predictive ability for recurrence was investigated among clinico-pathologic factors, BRAF mutation and FDG avidity of primary tumor using Cox proportional-hazards regression analysis.

Results Of the 412 patients, 19 (4.6%) experienced recurrence, which was confirmed either by pathology (n=17) or high serum thyroglobulin level (n=2), during the follow-up period of 43.9±16.6 months. Of the 412 patients, 237 (57.5%) had FDG-avid tumor and their mean SUVmax was 7.1±7.0 (range 1.6~50.5). In univariate analysis, tumor size (p=0.0030), FDG-avidity of primary tumor (p=0.0142), extrathyroidal invasion (p=0.0279), and pathological lymph node (LN) stage (p<0.0001) were significant predictors for recurrence. However, only LN stage remained as the significant predictor in multivariate analysis (p<0.0001). The primary tumor FDG-avidity was correlated with LN stage (p<0.0001), tumor size (p<0.0001), and extrathyroidal invasion (p<0.0001).

Conclusions LN stage was proved to be a single predictor of PTC recurrence in the current study. FDG-avidity of primary tumor was correlated with pathologic parameters including LN stage, which indicates the potential of preoperative FDG PET/CT regarding prognosis prediction of PTC.