Accuracy of FDG-PET Scanning to Diagnose Malignant Thyroid Nodules

While FNA is a sensitive test for diagnosing thyroid tumors, it cannot differentiate benign from malignant follicular nodules and sometimes yields equivocal results due to inadequate sampling or indeterminate cytology. The standard of care for patients with equivocal or follicular histology is surgical removal of these nodules, most of which are benign in nature. FDG-PET, as evidenced by our prior experience and studies from other groups, may have application in discriminating benign from malignant disease in these patients with equivocal or follicular FNA results using standardized uptake value determination. We have demonstrated the feasibility and preliminary clinical utility of using limited neck FDG-PET exams in patients with indeterminate thyroid nodules in a pilot study. The purpose of this trial is to prospectively evaluate a larger series of patients with equivocal or follicular histology on FNA to more accurately define the sensitivity and specificity of FDG-PET for diagnostic imaging of these nodules. In addition, the utility of this modality in identifying metastatic foci in patients with thyroid cancer having follicular or equivocal histology on FNA will be assessed. If the sensitivity and specificity of this modality are determined to be high (≥95%) for diagnosing malignant nodules in these patients, many patients with benign disease may potentially benefit by avoiding unnecessary operations.