Comparison of 99mTc-methoxyisobutyl isonitrile and 201Tl scintigraphy for detection of residual thyroid cancer after 131I ablative therapy.
In this study, we compared 99mTc-methoxyisobutyl isonitrile (MIBI) with 201Tl scintigraphy for the detection of residual thyroid cancer not found by 131I scans in patients with increased risk of recurrence after 131I therapy.


METHODS
201Tl and MIBI scans were obtained in 54 patients with negative 131I scans 3-25 y (median 7.9 y) after the first postsurgical 131I therapy. Serum thyroglobulin (Tg) levels were measured while patients were receiving thyroid hormone and again 6 wk after withdrawal of hormone therapy.


RESULTS
The overall results were the same for both 201Tl and MIBI imaging, with a sensitivity of 19 of 36 (53%), specificity of 17 of 17 (100%) and accuracy of 36 of 54 (69%). Planar images missed residual cancer in high cervical lymph nodes adjacent to salivary gland activity, in small nodes (<1 cm) deep in the neck or chest and with diffuse pulmonary micrometastases. Serum Tg was elevated in 24 of 36 (67%) patients with residual cancer; 201Tl detected tumor sites in 13 of 24 (54%) of these patients, and MIBI detected tumor sites in 14 of 24 (58%) of these patients. Of the 12 patients who had residual cancer and false-negative serum Tg levels, 6 had true-positive 201Tl and 5 had true-positive MIBI scans.


CONCLUSIONS
201Tl and MIBI planar imaging yield the same high specificity and positive predictive value for residual thyroid cancer in patients with high-risk profiles and negative radioiodide scans. Both imaging agents detected residual cancer in more than half of the patients in whom conventional staging techniques did not reliably detect either the presence or the extent of residual thyroid cancer and changed the management in patients with surgically resectable cancer.
Seabold
J E
JE
Department of Radiology, University of Iowa College of Medicine, Iowa City, USA.
Gurll
N
N
Schurrer
M E
ME
Aktay
R
R
Kirchner
P T
PT
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002291:Carcinoma, Papillary / Q000000981:diagnostic imaging* / Q000532:radiotherapy / Q000556:secondary* / Q000601:surgery; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008198:Lymph Nodes / Q000000981:diagnostic imaging; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D018365:Neoplasm, Residual; D011237:Predictive Value of Tests; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D012307:Risk Factors; D012680:Sensitivity and Specificity; D017256:Technetium Tc 99m Sestamibi; D013794:Thallium Radioisotopes; D013954:Thyroglobulin / Q000097:blood; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D013965:Thyroidectomy
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D013794:Thallium Radioisotopes; D013954:Thyroglobulin; D017256:Technetium Tc 99m Sestamibi