Clinical value of [18F]FDG-PET/CT in the detection of metastatic medullary thyroid cancer

PurposeTo evaluate the value of fluorine-18 2-deoxy-2-d-glucose positron emission tomography/computed tomography ([18F]FDG-PET/CT) in the detection of metastatic medullary thyroid cancer.MethodsFrom November 2006 to November 2012, 50 medullary thyroid cancer patients (median age 48.7years, range 18–76) who had a total thyroidectomy operation underwent whole-body [18F]FDG-PET/CT scans. The diagnostic accuracy of [18F]FDG-PET/CT was determined through both lesion-based and patient-based analyses. Further pathological tests were performed on all identified lesions or clinically followed for a minimum period of 6months.ResultsOne hundred forty-four suspicious lesions were identified by organ-based analysis. Of these lesions, [18F]FDG-PET/CT detected 99 true-positive lesions, sensitivity was 73.3%, and specificity was 66.7%. On the patient-based analysis, the overall sensitivity and specificity were calculated as 65.7% and 92.3%, respectively. Using a cutoff calcitonin value of 1000pg/ml, in patients with calcitonin lower than this value, sensitivity and specificity were 42.9% and 91.0%, respectively. In patients with calcitonin exceeding this value, they raised to 77.3% (χ2=4.392, P<.05) and 100% (χ2=0.197, P>.05), respectively. Compared with conventional imaging modality, PET/CT scans detected more lesions in 10 patients (20.4%) and correctly changed the treatment in 8 patients (16.3%).Conclusion[18F]FDG-PET/CT has excellent sensitivity and specificity, especially when the calcitonin value is higher than 1000pg/ml for detecting metastatic medullary thyroid cancer. Compared to conventional morphologic imaging methods, it provides additional information for diagnosis.