Comparison of the diagnostic and prognostic values of 99mTc-MDP-planar bone scintigraphy, 131I-SPECT/CT and 18F-FDG-PET/CT for the detection of bone metastases from differentiated thyroid cancer

The aim of this study was to compare the diagnostic and prognostic values of (99m)Tc-MDP-planar bone scintigraphy ((99m)Tc-MDP-BS), (131)I single-photon emission computed tomography/computed tomography ((131)I-SPECT/CT) and (18)F-fluorodeoxyglucose ((18)F-FDG)-PET/CT for the detection of bone metastases from differentiated thyroid cancer (DTC).Eighty patients with DTC with suspected bone metastases from DTC were retrospectively analysed. All patients were examined with (99m)(99m)Tc-MDP-BS, (131)I-SPECT/CT and (18)F-FDG-PET/CT, with a maximum interval of 2 months between scans. The diagnostic performances of (99m)Tc-MDP-BS, (131)I-SPECT/CT and (99m)F-FDG-PET/CT were investigated and compared. Univariate and multivariate analyses were carried out to evaluate the effects of variables on the survival of patients.Out of the 80 patients with 148 foci, 43 with 106 foci were diagnosed as being true positive for bone metastases from DTC. In patient-based analysis, the sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of (99m)Tc-MDP-BS were 79.07, 83.78, 85.00, 77.50 and 81.25%, respectively; those of (131)I-SPECT/CT were 93.02, 97.30, 97.56, 92.31 and 95.00%, and those of (18)F-FDG-PET/CT were 86.05, 94.59, 94.87, 85.36 and 87.80%, respectively. In lesion-based analysis, the sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of (99m)Tc-MDP-BS were 72.64, 73.81, 87.50, 51.67 and 72.97%, respectively; those of (131)I-SPECT/CT were 92.45, 97.62, 98.99, 83.67 and 93.92%, and those of (18)F-FDG-PET/CT were 85.85, 88.10, 94.50, 71.15 and 86.49%, respectively. Comparing the receiver-operating characteristic area using the McNemar test, both (131)I-SPECT/CT and (18)F-FDG-PET/CT were found to be superior to (99m)Tc-MDP-BS for the detection of bone metastases from DTC in patient-based and lesion-based analyses (P<0.05). Patient-based analysis showed that there were no significant differences between (131)I-SPECT/CT and (18)F-FDG-PET/CT (P=0.087) but lesion-based analysis revealed that (131)I-SPECT/CT was superior to (18)F-FDG-PET/CT (P=0.002). For the association between these image patterns and the prognosis of DTC patients, (18)F-FDG positivity was the factor predicting a poor prognosis.(131)I-SPECT/CT and (18)F-FDG-PET/CT demonstrated high diagnostic performance in detecting bone metastases from DTC. (99m)Tc-MDP-BS might be completely replaced by (131)I-SPECT/CT in combination with ((131)F-FDG-PET/CT in the management of DTC patients with bone metastases. (18)F-FDG-PET/CT positivity was an independent factor associated with poor prognosis.