~(99m)Tc-MIBI AND ~(131)I SCINTIGRAPHY IN THE FOLLOW-UP OF DIFFERENTIATED THYROID CARCINOMA (DTC) PATIENTS AFTER SURGERY

摘要

The MIBI scan has been reported to be a highly sensitive imaging technique for the detection of differentiated thyroid carcinoma (DTC) metastases that have lost the capability to uptake ~(131)I. The purpose of this study was to evaluate, retrospectively, the value of the ~(99m)Tc-MIBI scan and ~(131)I whole body scintigraphy using thyroglobulin (Tg) levels as a basis for comparison. A total of 84 patients with DTC (47 cases with papillary, 18 cases with follicular and 19 cases with papillary-follicular) were assessed. All of them had undergone total or near total thyroidectomy and received radioiodine treatment for ablation of post-surgical residual thyroid tissue. They were examined after 4 weeks L-thyroxin withdrawal in the follow-up of DTC. Planar and whole body images were acquired at 15 min and 180 min after IV application of ~(99m)Tc-MIBI (555-740 MBq) and at 48 h after post-operative administration of ~(131)I (111-185 MBq). Serum Tg assays were performed to clarify the presence of residual recurrent malignancy. The ~(131)I scan was positive in 55 patients, showing thyroid remnants in 31 cases, lymph node metastases in 24 cases, pulmonary metastases in 6 cases and bone lesions in 2 cases. In 18 patients the ~(131)I scan was negative, Tg was undetectable, and therefore the patients were considered tumour free. In 11 patients the ~(131)I scan was negative while serum Tg was increased. These false negative results were observed predominantly in cases with less differentiated metastatic cells, especially after several courses of high dose ~(131)I therapy. The ~(99m)Tc-MIBI scan revealed the presence of lymph node and/or lung metastases (non-functioning metastases) in 9 of them; false negative results were obtained in 2 cases. Serum Tg was increased in all patients with local lymph node and distant metastases, visualized by ~(131)I or by ~(99m)Tc-MIBI, but also in 18 patients with thyroid remnants only. Considering the ~(131)I scan as the most specific standard procedure the authors conclude that the combined ~(99m)Tc-MIBI scintigraphy and serum Tg assay appear to be an alternative to radioiodine diagnostic imaging to demonstrate the extent of the disease in cases with DTC and elevated Tg.