F18-fluorodeoxyglucose positron emission tomography in detecting metastatic papillary thyroid carcinoma with elevated human serum thyroglobulin levels but negative I-131 whole body scan.
Papillary carcinomas are the most common thyroid malignancies. They invade the regional lymphatics and metastasize frequently to local lymph nodes in the neck. Distant metastasis, generally to the lungs, is also common.


METHODS
The aim of this study is to evaluate the effectiveness of F18-fluorodeoxyglucose (FDG) positron emission tomography (PET) to detect metastatic lesions in patients with papillary thyroid carcinomas (PTC) after nearly total thyroidectomy and I-131 treatments who present with elevated human serum thyroglobulin (hTg) levels but negative 1-131 whole body scan (WBS). Twenty patients with PTC who underwent nearly total thyroidectomy and radioiodine treatments were included in this study.


RESULTS
All of the 20 patients had negative I-131 WBS results and elevated hTg levels (hTg > or = 2.0 microIU/mL) under thyroid-stimulating hormone (TSH) stimulation (TSH > or = 30 microIU/mL).


CONCLUSIONS
FDG-PET was perform to detect metastatic lesions. F18-fluorodeoxyglucose-PET could detect hypermetabolic lesions in 17 patients but failed to demonstrate miliary pulmonary metastases in two patients. No definite lesion was found in FDG-PET, x-ray chest computed tomography (CT) and other imaging studies of the remaining one patient This study showed that FDG-PET is a useful tool in detecting metastatic lesions in PTC with elevated hTg but negative I-131 WBS. However, miliary lung metastases may be missed in FDG-PET. In this circumstance, chest CT should be included in the follow-up protocol.
Hung
Min-Chang
MC
Department of Surgery, Show Chwan Memorial Hospital, Changhua, Taiwan.
Wu
Hurng-Sheng
HS
Kao
Chia-Hung
CH
Chen
Wen-Kang
WK
Changlai
Sheng-Pin
SP
D000328:Adult; D000368:Aged; D002291:Carcinoma, Papillary / Q000097:blood / Q000000981:diagnostic imaging* / Q000556:secondary; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000097:blood / Q000000981:diagnostic imaging* / Q000473:pathology; D014055:Tomography, Emission-Computed; D014915:Whole-Body Counting
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D013954:Thyroglobulin