Abstract:

Objective To investigate the value of 18F-fluorodeoxyglucose (18F-FDG) PET/CT imaging for detecting recurrent or metastatic foci of patients with differentiated thyroid carcinoma (DTC) and negative results of 131I-whole body scan. Methods A total of 178 patients with DTC who underwent thyroidectomy and 131I ablation of residual thyroid tissues and/or metastatic foci (results of cervical ultrasound or chest CT were persistent positive but results of 131I-whole body scan were negative during follow-up) were examined by 18F-FDG PET/CT imaging. Patients with suspicious foci and positive results of 18F-FDG PET/CT imaging underwent ultrasound-guiding aspiration biopsy or surgical resection. Values for predicting recurrent or metastatic foci by 18F-FDG PET/CT imaging at different levels of serum thyroglobulin (Tg) were analyzed using the results of pathological examinations as the golden criteria. Results A total of 77 patients with positive results of 18F-FDG PET/CT imaging were enrolled. Among them, 65 patients were pathologically confirmed as DTC metastases and 12 patients with false positive results of 18F-FDG PET/CT imaging were pathologically confirmed as inflammatory cell infiltration. Among 77 patients with positive results of 18F-FDG PET/CT imaging, 50 patients were serum Tg positive and 45 of them were pathologically confirmed as DTC metastases. For serum Tg positive patients, the rate for predicting the positive results by 18F-FDG PET/CT imaging was 90.00% (45/50). Among 27 serum Tg negative patients, 20 of them were pathologically confirmed as DTC recurrence or metastases. For serum Tg negative patients, the rate for predicting the positive results by 18F-FDG PET/CT imaging was 74.07% (20/27). Conclusion 18F-FDG PET/CT imaging is an effective examination method for patients with DTC who have suspicious recurrent or metastatic foci and negative results of 131I-whole body scan during follow-up.

Key words: differentiated thyroid carcinoma, fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography, 131I-whole body scan, thyroglobulin