Tc-99m MIBI SPECT in detecting metastatic papillary thyroid carcinoma in patients 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. The aim of this study is to evaluate the effectiveness of single photon emission computed tomography (SPECT) with technetium-99m methoxyisobutylisonitrile (Tc-99m MIBI) in detecting metastatic lesions in patients with papillary thyroid carcinoma (PTC) after nearly total thyroidectomy and radioiodine (I-131) treatment who present with elevated serum human thyroglobulin (hTg) levels but negative I-131 whole body scan (WBS).


METHODS
Twenty patients of PTC who underwent nearly total thyroidectomy and I-131 treatments were included in this study. All of the 20 patients had negative I-131 WBS results and elevated hTg levels (hTg > or = 20 microIU/mL) under thyroid-stimulating hormone (TSH) stimulation (TSH > or = 30 microIU/mL). Technetium-99m MIBI SPECT was performed to detect metastatic lesions.


RESULTS
Technetium-99m MIBI SPECT demonstrated lesions in 10 patients. Technetium-99m MIBI SPECT failed to demonstrate lesions in nine patients including small lymph node and lung metastases.


CONCLUSIONS
This study showed that Tc-99m MIBI SPECT is a useful tool to detect metastatic lesions in PTC with elevated hTg but negative I-131 WBS. However, small lymph node and lung metastases may be missed in Tc-99m MIBI SPECT. In the latter circumstance, other imaging studies should be included in the follow-up protocol.
Hsu
Chung-Huei
CH
Department of Nuclear Medicine and Internal Medicine, Taipei Medical University Hospital, Taipei, Taiwan.
Liu
Feng-Yuan
FY
Yen
Ruoh-Fang
RF
Kao
Chia-Hung
CH
D000328:Adult; D000368:Aged; D002291:Carcinoma, Papillary / Q000097:blood / Q000000981:diagnostic imaging* / Q000556:secondary; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012680:Sensitivity and Specificity; D017256:Technetium Tc 99m Sestamibi; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000097:blood / Q000000981:diagnostic imaging* / Q000556:secondary; D015899:Tomography, Emission-Computed, Single-Photon
D007457:Iodine Radioisotopes; D013954:Thyroglobulin; D017256:Technetium Tc 99m Sestamibi