Role of 18F-fluorodeoxyglucose positron emission tomography/computed tomography in patients affected by differentiated thyroid carcinoma, high thyroglobulin level, and negative 131I scan: review of the literature

Abstract

Differentiated thyroid carcinoma (DTC) is a slow-growing tumor that represents 1% of all malignant tumors and is the most frequent endocrine cancer. ¹⁸F-Fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT) imaging is an increasingly important imaging tool in oncology and is still under investigation in numerous studies looking into its efficacy and cost-effectiveness. Despite the fact that ¹⁸F-FDG-PET/CT has been shown to be a powerful and accurate diagnostic tool in patients affected by DTC with high serum thyroglobulin (Tg) levels and negative radioiodine (¹³¹I) total body scan, its definitive role is not completely clear, in particular regarding the role of thyroid stimulating hormone (TSH) and Tg value "cutoff" over which is better to perform the study. In this review, these issues are analyzed to clarify controversial aspects and identify established cornerstones. In particular, the literature analysis suggests that levothyroxine withdrawal is preferable in cases of relatively low Tg levels (<10 ng/ml) and good clinical compliance to hypothyroidism. Moreover, recombinant thyrotropin stimulating hormone (rTSH) could be a preferable alternative in patients clinically unable to tolerate therapy withdrawal. A Tg cutoff level over which to perform the study seems to be 10 ng/ml, a reasonable value maintaining high accuracy in terms of a good compromise between sensitivity and specificity.

Detection of Subcentimeter Metastatic Cervical Lymph Node by 18F-FDG PET/CT in Patients With Well-Differentiated Thyroid Carcinoma and High Serum Thyroglobulin But Negative 131I Whole-Body Scan

“…There was evidence that there is a positive correlation between higher Tg level and higher accuracy of PET/CT. 12 Thyroglobulin levels more than 10 ng/mL could enhance the diagnostic value of PET/CT, and the highest accuracy occurred when performed in patients with a Tg level of more than 21 ng/mL. 27 The difference in the type of surgery and varying criteria of false-negative can also affect the sensitivity as mentioned in the discussion of lesion-based analysis and the study's limitations.…”

The use of 18F-fluorodeoxyglucose positron emission tomography combined with computed tomography in patients with differentiated thyroid cancer after initial treatment

“…Bertagna и соавт., проведя обзор литературы по поводу связи ПЭТ / КТ с уровнем ТГ, пришли к вы-воду, что уровень среза (cutoff level) ТГ в 10 нг / мл яв-ляется обоснованным, отражаясь в высокой точности метода с точки зрения хорошего сочетания чувстви-тельности и специфичности [52].…”

99mTc-EDDA/HYNIC-TOC in the diagnosis of differentiated thyroid carcinoma refractory to radioiodine treatment

“…For many years PET-CT using 18-fluoro-deoxyglucose ( 18 F-FDG) has been successfully used in the detection of non-iodine avid DTC recurrence [9,10]. Sensitivity of PET-CT in population of DTC patients with elevated Tg and negative WBS is estimated between 69 and 95%, especially when performed in the conditions of TSH stimulation [11][12][13][14][15][16].…”