This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.Well-differentiated epithelial thyroid cancer has an incidence of 20,000 cases per year in the U.S., the vast majority of whom undergo successful primary treatment. However approximately one-third of patients suffer recurrent disease, sometimes decades later.Surgery, postoperative radioactive iodine, and long-term TSH-suppressive thyroxine therapy are the mainstays of treatment. Radioiodine scanning has traditionally been the primary mode for detection of residual thyroid cancer tissue. However, tumors often lose sufficient iodine avidity to be detected with conventional radioiodine scanning. In the vast majority of these patients, residual disease is evidenced by presence of a circulating thyroid-specific tumor marker: thyroglobulin. These 'thyroglobulin-positive' patients may benefit from other therapies, including surgery, external beam irradiation, and occasionally chemotherapy; but their extent of disease and its location must be defined. In some patients sonography, CT and MR examinations followed by biopsy can localize disease; but it remains unidentified by these techniques in approximately one-third of these patients.18-Fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) has been shown to detect residual thyroid carcinoma in approximately two-thirds of patients with detectable thyroglobulin, but negative 1-131 scans. Recombinant TSH (rTSH) has previously been used in thyroid carcinoma patients to stimulate both 1-131 uptake for diagnostic radionuclide scanning and thyroglobulin production. TSH is also know to increasing glycolytic activity in cultured thyrocytes. Consequently, this two-center prospective study is designed to test the hypothesis that rTSH-stimulated glucose metabolism in thyroid cancer tissue will improve the sensitivity of FDG PET for localizing and quantifying residual disease. The protocol also evaluates the impact of PET-CT fusion scanning, which permits the co-localization of hypermetabolic activity with anatomic features. It is proposed that use of this novel technique will enhance identification of residual thyroid cancer tissue and facilitate the implementation of rationale secondary treatment strategies.
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