ABSTRACT
ABSTRACT: Differentiated thyroid carcinoma (DTC) has an excellent prognosis with a 10-year survival rate higher than 90%. However, persistent or recurrent disease occurs in 5 to 24% of patients. Patients with increasing serum thyroglobulin (TG) values and negative diagnostic 131I (RAI) whole body scan (WBS) results should undergo appropriate imaging modalities to localize the disease and plan adequate treatment. Recently, 18FDG positron emission tomography/computed tomography (PET/CT) has been proposed as a useful imaging modality to study these patients. The aim of this report is to evaluate the rational use of PET/CT as a diagnostic and therapeutic tool for patients with DTC recurrence. One hundred DTC patients underwent thyroidectomy and postoperative thyroid remnant ablation with 131I and were studied using PET/CT because of rising basal or recombinant thyroid-stimulating hormone (TSH)-stimulated serum TG levels. The patients were divided into three groups based on the indication for PET/CT: diagnostic indication for patients with
RAI negative WBS and increased TG levels (group 1), surgical planning for patients with known recurrence (group 2), and prognostic or therapeutic efˆcacy evaluation for patients with advanced disease (group 3). PET/CT positive foci were found in 53 of 100 studies. In group 1 (N = 33), PET/ CT localized recurrent disease in 42% of patients. In group 2 (N = 45), PET/CT scan predicted loco-regional resectable disease in 42% of patients. In group 3 (N = 22), PET/CT conˆrmed sites of known metastatic disease in 59% of cases. PET/CT results led to surgical treatment with radical intent in 19 patients (complete remission in 8 patients) and palliative intent in 6 cases. In addition,
11.1 Introduction .......................................................................................................................... 184 11.2 Material and Methods ........................................................................................................... 185
11.2.1 Patients ...................................................................................................................... 185 11.2.2 18FDG PET-CT Protocol ........................................................................................... 185
11.3 Results ................................................................................................................................... 186 11.3.1 Clinical Indications for PET/CT ............................................................................... 186 11.3.2 Results of PET/CT in Group 1 .................................................................................. 187 11.3.3 Results of PET/CT in Group 2 .................................................................................. 188 11.3.4 Results of PET/CT in Group 3 .................................................................................. 189
11.4 Discussion ............................................................................................................................. 190 References ...................................................................................................................................... 191
PET/CT results led to high-dose RAI treatment for 11 patients and external beam radiotherapy for 3 patients. The remaining 14 patients underwent only clinical follow-up. The study emphasizes how PET/CT indications are changing from a purely diagnostic role in localizing RAI negative DTC recurrences to designing appropriate DTC surgical or combined therapeutic strategies.
