ABSTRACT
Objective[s]: In clinical practice, approximately 10-25% of post-surgical differentiated thyroid carcinoma [DTC] patients with high serum thyroglobulin [Tg] and negative [131]I whole-body scan [WBS] have poor prognosis due to recurrent or metastatic lesions after radioactive iodine treatment. The purpose of this study was to evaluate the value of [18]F-FDG PET/CT scan in DTC patients with high serum Tg level and negative [131]I WBS
Methods: 69 post-surgical DTC patients with high serum Tg level and negative post ablation [131]I WBS were enrolled in this study. All DTC patients underwent head and neck ultrasound, CT scan and whole-body [18]F-FDG PET/CT, based on the dedicated head and neck protocol
Results: Overall, 92 lesions were detected in 43 [62.3%] out of 69 patients with positive [18]F-FDG PET/CT scan, compared to only 39 lesions detected on CT scan in 26 [37.7%] out of 69 patients. The sensitivity, accuracy and negative predictive value of [18]F-FDG PET/CT were 88%,87% and 76%, respectively, which were significantly higher than those of CT scan [67.2%, 54.3% and 48.8%, respectively] [P<0.01]. Specificity and positive predictive value of [18]F-FDG PET/CT [90.5% and 95.2%, respectively] were similar to those of CT scan [95.2% and 96.2%, respectively] [P>0.05]. The maximum standardized uptake value [SUV[max]] threshold was 4.5 with a good diagnostic value [sensitivity of 92.3% and specificity of 100%]. The dedicated head and neck [18]F-FDG PET/CT protocol altered the treatment plan in 33 [47.8%] out of 69 DTC patients with high serum Tg level and negative [131]I WBS
Conclusion: Dedicated head and neck [18]F-FDG PET/CT protocol showed a higher diagnostic value, compared to CT scan and played an important role in detecting recurrent or metastatic lesions in post-surgical DTC patients with high serum Tg level and negative [131]I WBS