RESUMO
Objective To investigate the diagnostic value and the impact on treatment decision of 18F-FDG PET/CT in differentiated thyroid carcinoma (DTC) patients with elevated serum thyroglobulin (Tg) levels and negative radioiodine 131I post-therapy whole body scan (131I-RxWBS).Methods Totally 72 patients with DTC who had elevated serum Tg levels and negative 131I-RxWBS were enrolled,and 18F-FDG PET/CT was performed.The imaging results of 18F-FDG PET/CT were compared with the clinical results of surgical pathology or 6 to 36 months follow up.The diagnostic efficacy of 18F-FDG PET/CT in detection of recurrence and/or metastasis of DTC with elevated Tg levels and negative 131I-RxWBS was evaluated.Results The accuracy,sensitivity,specificity,positive prediction value and negative prediction value of 18F-FDG PET/CT in diagnosis of DTC with elevated Tg levels and negative 131I-RxWBS was 83.33％ (60/72),89.47％ (34/38),76.47％ (26/34),80.95％ (34/42) and 86.67％ (26/30),respectively.18F-FDG PET/CT changed the treatment strategies of 35 patients (35/72,48.61 ％) among 72 patients,while recurrence or metastasis of DTC was not found during clinical follow-up in 23 of these 35 patients (23/35,65.71％) who underwent reoperation,but was detected in the other 12 patients (12/35,34.29％).Conclusion 18F-FDG PET/CT is a valuable method for detection of recurrence and/or metastasis of DTC with elevated Tg levels and negative 131I-RxWBS,also for guiding the follow-up treatment strategy.