The clinical significance of (18)F-FDG-PET/CT in the follow-up of patients with differentiated thyroid carcinoma was evaluated and the results were compared with those of (18)F-FDG-PET, (131)I-whole-body scintigraphy including SPECT/CT (WBS) and ultrasound. In addition, it was the aim to investigate the impact of (18)F-FDG-PET/CT on the therapeutic management.
Patients, methods: 327 patients (209 women, 118 men; mean age 53 ± 18 years) with differentiated thyroid cancer (242 papillary, 75 follicular, 6 mixed, 1 Hürthle cell and 3 poorly differentiated tumours) were analyzed retrospectively at four tertiary referral centres. 289 (18)F-FDG-PET/CT and 118 (18)F-FDG-PET studies were performed in these patients between 2007 and 2010. In addition, an overall clinical evaluation was performed, including cytology, histology, thyroglobulin level, ultrasound, WBS, and subsequent clinical course in order to compare the molecular imaging results. Finally, the change in therapeutic management due to findings of (18)F-FDG-PET/CT was investigated.
Results: The sensitivity of (18)F-FDG-PET/CT was 92%, the specificity was 95%. Sensitivity and specificity of (18)F-FDG-PET alone were 67% and 93%, respectively. WBS showed a sensitivity of 65% and a specificity of 94%. The corresponding values of ultrasound were 37% and 94%, respectively. The sensitivity of (18)F-FDG-PET/CT in the group of patients with a negative WBS (n=194) amounted to 96%. When (18)F-FDG-PET/CT and WBS were considered in combination, tumour tissue was missed in only 2 out of 133 patients; when (18)F-FDG-PET and WBS were combined, tumour tissue was missed in 1 out of 24 patients. (18)F-FDG-PET/CT resulted in management change in 43% (n=57/133) with a decision on surgical approach in 20% (n=27/133).
Conclusions: (18)F-FDG-PET/CT is superior to (18)F-FDG-PET alone in patients with differentiated thyroid cancer and has a direct impact on the therapeutic management of patients with suspected local recurrence or metastases, particularly in those with negative WBS.