99mTc-sestamibi and 131I whole-body scintigraphy and initial serum thyroglobulin in the management of differentiated thyroid carcinoma.
99mTc-sestamibi whole-body scanning has been used in the postoperative assessment of differentiated thyroid carcinoma together with 131I whole-body scanning and serum thyroglobulin (Tg) estimation. This study compared 99mTc-sestamibi whole-body scanning with 131I whole-body scanning in the context of initial serum Tg levels of patients after total or near-total thyroidectomy who were taken off thyroxine suppression therapy and who had no 131I ablation before surgery.


METHODS
A prospective study of 360 patients was undertaken. 99mTc-sestamibi whole-body scintigraphy was performed at least 5 wk after thyroidectomy and was followed by 131I whole-body scanning. The patients had no thyroxine suppression for 5 wk, and Tg was measured thereafter. Radiologic studies (chest radiography, CT, MRI, sonography, and bone scanning) and histopathologic examinations were performed to clarify the presence of metastases with positive uptake on either 99mTc-sestamibi scans or 131I whole-body scans. Positive scans were defined as those with the presence of thyroid remnants, lymph node disease, or metastases.


RESULTS
Two hundred fifty-nine (71.9%) of the 360 patients had initial serum Tg levels < 30 ng/mL (group 1), whereas 101 (28.1%) had initial serum Tg levels > or = 30 ng/mL (group 2). Of the 259 group 1 patients, 82 had positive 99mTc-sestamibi scans and 113 had positive 131I scans; 71.7% of patients with positive 1311 scans also had positive 99mTc-sestamibi scans, and 98.8% of patients with positive 99mTc-sestamibi scans also had positive 131I scans. Of the 101 group 2 patients, 81 had positive 99mTc-sestamibi scans and 97 had positive 131I scans; 83.5% of patients with positive 131I scans also had positive 99mTc-sestamibi scans, and all patients with positive 99mTc-sestamibi scans also had positive 131I scans. Of those with initial serum Tg levels > or = 30 ng/mL (group 2), 27.2% had thyroid remnants and 68.8% had lymph node disease or metastases. 131I scanning detects more thyroid remnants and lung metastases than does 99mTc-sestamibi scanning.


CONCLUSIONS
Our findings suggest that, compared with 131I scanning, 99mTc-sestamibi scanning is less sensitive in detecting thyroid remnants and lung metastases but appears to be more useful in the detection of lymph node disease before initial 131I treatment.
Ng
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Department of Nuclear Medicine, Singapore General Hospital, Singapore.
Sundram
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Sin
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D003952:Diagnostic Imaging; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007457:Iodine Radioisotopes; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity; D017256:Technetium Tc 99m Sestamibi; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging; D013965:Thyroidectomy
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D013954:Thyroglobulin; D017256:Technetium Tc 99m Sestamibi