TECHNETIUM-99M-TETROFOSMIN WHOLE-BODY SCINTIGRAPHY IN THE FOLLOW-UP OF DIFFERENTIATED THYROID-CARCINOMA

The purpose of this study was to evaluate prospectively the reliabilit y of the new nonspecific tumor-searching tracer tetrofosmin in the pos toperative follow-up of differentiated thyroid carcinoma (DTC) during TSH suppressive thyroid hormone treatment, Methods: Whole-body scintig raphy was performed in 114 patients under TSH suppressive L-T4 treatme nt 20 min after intravenous injection of 370 MBq Tc-99m-tetrofosmin by means of a dual-head gamma camera followed by three-dimensional SPECT in case of suspicious tracer uptake, The results of serum thyroglobul in, ultrasonography of the neck, I-131 whole-body scintigraphy, chest radiograph, transmission GT or MRI, and bone scintigraphy were also av ailable, Results: A group of 68 patients without thyroid remnants who were tumor free and had no history of metastases or tumor recurrence s howed a negative Tc-99m-tetrofosmin whole-body scan. Another 24 patien ts (papillary carcinoma pT1NOMO) were also in complete remission, but had sonographically proven remnants (echonormal), Sixteen of them (67% ) exhibited Tc-99m-tetrofosmin accumulation in the thyroid bed, which corresponded excellently to the localization of the remnant, The third group comprises seven cases of local recurrence confirmed by histopat hology after reoperation or by cytology after fine-needle aspiration w here tetrofosmin scintigraphy clearly revealed relapse of malignancy i n all cases, A total of 17 patients had distant metastases (11 pulmona ry, 3 bone, 2 bone and pulmonary, I bone and soft tissue) discovered b y different modalities, resulting in 44 lesions to be evaluated, Of th e 23 radioiodine negative metastases, 17 were detected by tetrofosmin (74%), whereas all 21 radioiodine accumulating lesions also showed tet rofosmin positive scans. The overall sensitivity of Tc-99m-tetrofosmin in detecting distant metastatic lesions was 86%. Four additional case s with radioiodine-negative disseminated lung metastases showed diffus e pulmonary tetrofosmin uptake, Conclusion: Technetium-99m-tetrofosmin is a promising tracer to detect malignant recurrence and distant meta stases in the follow-up of DTC without the necessity of thyroid hormon e withdrawal.