Therapeutic impact of 18FDG-PET/CT in the management of iodine-negative recurrence of differentiated thyroid carcinoma.

Background: 18-F-fluoro-2-deoxyglucose positron emission tomography ((18)FDG-PET) is useful in the detection of iodine-negative differentiated thyroid carcinoma (DTC). The aim of this prospective study was to assess therapeutic impact of (18)FDG-PET imaging using a PET/computed tomography (CT) system in patients with iodine-negative recurrence of DTC.

Methods: From 2002 to 2006, patients with recurrence of DTC diagnosed by elevated thyroglobulin level and negative 131-I whole-body scan were included.

Results: Forty-five patients (31 women, 14 men), with a mean age of 55 years, with 36 papillary, 5 follicular, and 4 Hürthle carcinomas, were studied. All patients had previously undergone total thyroidectomy and postoperative thyroid remnant ablation with 131-I. The findings of (18)FDG-PET/CT were positive in 31 patients (68.8%) and negative in 14 (32.2%). Results were true positive in 24 of 31 patients. The sensitivity, positive predictive value, and accuracy of (18)FDG-PET/CT were 63%, 77%, and 53%, respectively. Twenty patients were operated on, 19 had neck surgery with mediastinal lymph node dissection (1 case) and lung resection (1 case), and 1 underwent lung resection. Seven patients had a stimulated thyroglobulin level <1 ng/mL.

Conclusion: (18)FDG-PET/CT is able to select patients who can benefit from surgery. Normalization of thyroglobulin is observed in one third of operated patients.