Clinical relevance of 18 F-FDG PET/CT in the postoperative follow-up of patients with history of medullary thyroid cancer

The aim of the study was evaluation of F-fluorodeoxyglucose ( F-FDG) positron emission tomography with computed tomography (PET/CT) in the detection of active disease in the patients with suspected recurrence of the medullary thyroid carcinoma (MTC). F-FDG PET/CT investigation was performed in 67 patients, investigated from 2010 to 2019. _ Follow up was performed from 6 to 116 months after surgery (median 16.5 months, x± SD = 29±28.9 months). Twenty five of 67 patients underwent Tc-dimercaptosuccinic acid ( Tc-DMSA) scintigraphy, 11 underwent somatostatin receptor scintigraphy (SRS) with Tc-HYNIC TOC while 11 I-metaiodobenzylguanidine (MIBG) scintigraphy. From 67 patients, 35 (52.2%) had true positive F-FDG PET/CT findings (TP). Average maximal standardized uptake value (SUVmax) for all TP lesions was 5.01+3.6. In 25 (37.3%) patients findings were true negative (TN). Four (6%) patients had false positive (FP) findings while three (4.5%) were false negative (FN). Thus, sensitivity of the F-FDG PET/ CT was 92.11%, specificity 86.21%, positive predictive value 89.74%, negative predictive value 89.29% and accuracy 89.55%. In 27 patients (40%) F-FDG PET/CT finding influenced further management of the patient. F-FDG PET/CT has high accuracy in the detection of metastases/recurrences of MTC in patients after thyroidectomy as well as in evaluation and the appropriate choice of the therapy.