Imaging of locally recurrent and metastatic thyroid cancer with positron emission tomography

Serum thyroglobulin and imaging have been routinely used in the evaluation of thyroid cancer patients suspected of having metastatic or recurrent dise ase. A more sensitive technique capable of identifying the sites of disease not detected by current imaging methods might improve overall management. The objective in this study was to demonstrate the feasibility of using pos itron emission tomography (PET) for the detection of recurrent thyroid canc er. Thirty patients with a history of either papillary/follicular or medull ary thyroid cancer suspected of having locally recurrent or metastatic canc er on the basis of elevated or rising blood markers were evaluated with PET . Imaging studies were performed with the radiotracer [F-18] fluorodeoxyglu cose (FDG). A retrospective review of other imaging results was performed a nd compared to the PET results. PET was able to identify locally recurrent or metastatic papillary/follicular disease in all 24 patients studied with elevated or rising thyroglobulin. Similar results were obtained in 6 patien ts with medullary cancer recurrences in the presence of elevated calcitonin . In cases where follow-up data was obtainable (17/24 papillary/follicular cancers and 4/6 medullary cancers), disease was confirmed either directly b y surgery and/or indirectly through changes or persistence of laboratory fi ndings. The results support the hypothesis that in the presence of elevated blood markers indicative of recurrent thyroid cancer, PET may prove valuab le as an adjunctive imaging test for identifying disease and influencing ma nagement in cases where conventional imaging fails to detect suspected dise ase.