Diagnostic Approach to De-differentiated Thyroid Cancer

Abstract

Thyroid carcinoma is the most prevalent endocrine malignancy. More than 90% of TCs are well-differentiated that usually curable or controllable by the combination of surgery, radioiodine ablation, and TSH-suppressive therapy. However when thyroid cancer cells lose their basic biological characteristics this is called Cell De-differentiation, which is genetically based complex process that produces multiple molecular changes it occur in ~ 5% of cases and usually accompanied by more aggressive growth, metastatic spread, and inability to trap iodide, making the tumor resistant to radioiodine ablation and poorly responsive to conventional therapy.It is believed that the presence of the BRAFV600E mutation significantly reduces (NIS) expression and radioiodine uptake. Overexpression of tyrosine kinase (TK) receptors, in TC cells, open a new era in therapeutic clinical trial of TK inhibitors in refractory thyroid cancer, which has poor prognosis and lower survivals. Therefore, advanced deDTC represent a diagnostic and therapeutic challenge.Accurate diagnostic recurrent tumor localization is very important, especially when surgical intervention is considered. The fusion of the metabolic and morphologic information in PET/CT was able to increase the diagnostic accuracy, reduces pitfalls and changes therapeutic strategies in a considerable number of patients. FDG uptake and the concomitant loss of 131I uptake are known as a functional sign of dedifferentiation. The intensity of FDG uptake is correlated with progressive dedifferentiation, & worse prognosis. Over expression of GLUT1 on the cell membrane of thyroid neoplasm has been shown to be closely related to more grade of dedifferentiation. In a meta-analysis of 25 studies that included 789 patients, the sensitivity of FDG-PET/CT was 83% (ranging from 50 to 100%) and the specificity was 84% (ranging from 42 to 100%) in non 131I avid TC.Finally, PET/CT is able to improve diagnostic accuracy in a therapeutically relevant way in patients with deDTC.