Evaluation of suspected recurrent papillary thyroid carcinoma with [18F]fluorodeoxyglucose positron emission tomography

We evaluated 10 patients with suspected recurrent papillary thyroid cancer using [F-18]fluorodeoxyglucose positron emission tomography (FDG PET). Prior therapy included total (n = 8) or subtotal (n = 2) thyroidectomy, radiation therapy (n = 2) and radioiodine ablation (n = 2). All patients had an I-131 scan and one or more of the following imaging studies: Tc-99(m)-sestamibi scan, In-111-octreotide scan, sonography (US), computed tomography (CT) and magnetic resonance imaging (MRI). Both the PET and I-131 scans were negative in four patients. The PET and I-131 scan results were discordant in six patients. Of the six discordant cases, five had true-positive PET scans and false-negative I-131 studies. Three of these patients underwent neck lymph node dissection that showed positive histology for metastatic papillary carcinoma. noma. Another patient had fine-needle aspiration (FNA) of a parapharyngeal mass that was also positive for papillary carcinoma. One patient was treated with radiation to the thyroid surgical bed based on an elevated serum thyroglobulin and a positive PET finding. Tumour response with a decrease in the size of the lesion was documented by a follow-up MRI scan. The remaining patient had a presumed false-positive PET scan, since a difficult hypocellular FNA of a small palpable lymph node was negative for tumour. We conclude that FDG PET is useful in the evaluation of patients with suspected recurrent papillary thyroid cancer when the I-131 scan is negative. ((C) 1998 Lippincott-Raven Publishers).