PET-CT Scanning in the Management of Differentiated Thyroid Carcinoma

Purpose: Differentiated thyroid carcinoma (DTC) has a good prognosis with a 10-year survival rate higher than 90%. However, 5-24% of patients experience persistent or recurrent disease. DTC management guidelines recommend PET for imaging patients with 131I negative whole body scans and increasing serum thyroglobulin levels. The aim of this study was to assess the impact of PET on the therapeutic management of patients with recurrent DTC. Methods and Materials: 100 DTC patients underwent surgery and postoperative thyroid remnant ablation with 131I and were studied using PET-CT because of rising basal or recombinant TSH-stimulated serum thyroglobulin levels. They were divided into 3 groups based on: diagnostic indications for 131I-negative scanning and increasing thyroglobulin level (group 1, 33 pts); surgical planning for recurrent disease (group 2, 45 pts); and effectiveness of systemic therapy (group 3, 22 pts). Results: PET-positive foci were found in 53/100 studies. PET located recurrent disease in 42% of group 1 patients, predicted curative resection in 58% of group 2 patients, and confirmed known metastatic disease in 59% of group 3 patients. PET results led to surgical treatment with radical intent in 19 patients (complete remission in 8 patients) and palliative in 6 cases. Moreover, PET results led to high-dose 131I radio-metabolic treatment for 11 patients and external beam radiotherapy for 3 patients. The remaining 14 patients underwent only clinical follow‑up. Conclusion: The study emphasises how PET indications are changing from a purely diagnostic role in localising 131I-negative DTC recurrences to designing appropriate DTC surgical or combined therapeutic strategies.