The best TG cut-off value for 18F-FDG PET/CT imaging of de-differentiated thyroid cancer with elevated TG and negative 131-RAI WBS | ||||
| Egyptian Journal Nuclear Medicine | ||||
| Volume 28, Issue 1, June 2024, Page 41-55 PDF (641.16 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/egyjnm.2024.271575.1092 | ||||
 View on SCiNiTO | ||||
| Authors | ||||
Hoda Anwar   1; Sharmin Sultana1; AbdAllah El Taweel1; Mona Saied2
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| 1Nuclear Medicine Unit - Department of Clinical Oncology and Nuclear Medicine - Faculty of Medicine - Cairo University | ||||
| 2Nuclear Medicine unit, Clinical oncology and Nuclear Medicine department, Faculty of Medicine, Cairo University, Cairo, Egypt | ||||
| Abstract | ||||
| Objective: to determine the most appropriate threshold for thyroid cancer tumor indicators (TG and Anti-TG) among individuals who exhibited negative I131-WBS and rising tumor marker levels during follow-up who have clinical suspicion of de-differentiation and are therefore referred for 18F-FDG PET/CT scan. Methods: We looked at 31 patients' FDG PET/CT scans of thyroid carcinoma that was well-differentiated at the time of thyroidectomy, but their RAI WBS became negative during follow-up, in spite of rising TG or Anti-TG levels. Results: PET/CT was positive in in 21 patients and was negative in 10 patients. Patients whose PET/CT results were positive had TG values that were significantly different from those whose results were negative (p=0.006), but there was no statistically significant difference in the Anti-TG values between those whose PET results were positive and those whose were negative (p=0.29). A solid predictor of a positive PET/CT result is serum TG level, according to ROC-curve study for the optimal TG level before PET/CT, which showed an area under the curve (AUC) of 81%. The ideal detection limit is 25 ng/ml, which provides a sensitivity of 81%, a specificity of 60% percent and an overall accuracy of 74 %. An area under the curve (AUC) of 63% was shown by the ROC-curve analysis for the optimal Anti-TG level before PET/CT, indicating that serum TG level is a poor predictor of a positive PET/CT outcome. An estimated 27 ng/ml was the ideal level for the Anti-TG, with a sensitivity of 58%, specificity of 67 %, and an overall accuracy of 61 %. Conclusion: Patients with suspicion of de-differentiation after an initial diagnosis of differentiated thyroid cancer might benefit from PET/CT as a diagnostic tool. Nevertheless, our findings suggest that the optimal TG level for PET/CT to reliably detect a positive result is more than 25 ng/ml. | ||||
| Keywords | ||||
| De-differentiated thyroid cancer; PET; Thyroglobulin | ||||
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