Evaluation of 18fluoro-2-deoxyglucose positron emission tomography in iodine scan negative, differentiated thyroid cancer recurrence.

Background: Follow up of patients with differentiated thyroid cancer is based upon anatomical imaging, thyroglobulin assay and functional imaging in the form of iodine uptake scanning. A significant cohort of such patients have rising thyroglobulin levels but negative iodine scans. In this group, 18 fluoro-2-deoxyglucose positron emission tomography scans have been commonly employed. The aim of this study was to assess the usefulness of such investigation. Methods: The sensitivity of 18 fluoro-2-deoxyglucose positron emission tomography for detecting recurrence of differentiated thyroid cancer was calculated from a retrospective review of scan results from patients with iodine scan negative recurrence. Results: Eighteen patients with rising thyroglobulin levels underwent 18 fluoro-2-deoxyglucose positron emission tomography scanning. Fourteen patients had negative (and four equivocal) whole body iodine scintigraphy scans. Of these 14, six patients had a positive 18 fluoro-2-deoxyglucose positron emission tomography scan, giving a sensitivity of 42.9 per cent. Conclusions: When assessed in the clinical setting and restricted to patients with negative iodine scans, the sensitivity of 18 fluoro-2-deoxyglucose positron emission tomography was found to be lower than in previous case series.