Is TI-RADS classification and Score Modified Method of thyroid nodules can be effective for evaluation of Thyroid Incidentalomas on FDG PET-CT imaging

Background: Flourodeoyglucose Positron Emission Tomography-Computed Tomography (FDG PET-CT) provides information about the anatomic structures and metabolic activities of tumors. The incidence of thyroid incidentaloma is rare on FDG PET-CT but it is related to malignancy when it is detected to be high. Although, patients who are already treated with another primary tumor can not be searched for second thyroid malignancy each time. The aim of this study was to evaluate TI RADS classification based on a score modified according to ultrasound (US) criteria for malignancy of thyroid nodules determined on FDG PET/CT imaging.Materiels & Methods: Patients’ data diagnosed with a variety of cancer evaluated, retrospectively. All patients underwent PET/ CT examinations for cancer screening, staging, restaging, and detection of suspected recurrence. Patients with thyroid nodules on CT imaging provided by PET/ CT were selected.Results: Patients are divided into two groups. Group I included a total of 29 patients (24 women/ 5 men-age range: 30-80 years-mean age:57) with thyroid final histopathology results. Group II included a total of 24 (18 women/6 men-age range: 47-80, mean: 66.6) patients without pathology results of thyroid nodules. Of the 29 patients in group I, 20 patients had benign (69%) and 9 patients had malign (31%) histopathology results. Mean SUV max value in benign and malignant thyroid nodules were 5.3 (Range: 1-18) and 17.54 (Range: 7-35), respectively. Mean maximum standardized uptake value in malignant thyroid lesions was higher than that of benign lesions (P< 0.0001). Most of the benign thyroid nodules (85%) had TI RADS 1-3 classification while most malignant nodules had TI RADS 4-6 (87.5%). Mean SUV max value in thyroid nodules were 5.35 (Range: 1-43) in Group II follow-up patients. Thyroid nodules were TI RADS 1-5 classification in this group, most of which were 1-3 as benign thyroid nodules in group I patients. This group consisted of patients who could not have a thyroid biopsy due to primary malignancy diagnoses and advanced stages. None of them were diagnosed for thyroid malignancy or progressed during follow-up. Conclusions: Patients who do not have short expected duration of life due to other primary tumors should be evaluated with US. TI RADS classification based on a score modified according to ultrasound criteria for malignancy of thyroid nodules determined on FDG PET/CT imaging can be used for oncological patients.