Technetium-99m-tetrofosmin whole-body scintigraphy in the follow-up of differentiated thyroid carcinoma.

UNLABELLED: The purpose of this study was to evaluate prospectively the reliability of the new nonspecific tumor-searching tracer tetrofosmin in the postoperative follow-up of differentiated thyroid carcinoma (DTC) during TSH suppressive thyroid hormone treatment.

METHODS: Whole-body scintigraphy was performed in 114 patients under TSH suppressive L-T4 treatment 20 min after intravenous injection of 370 MBq 99mTc-tetrofosmin by means of a dual-head gamma camera followed by three-dimensional SPECT in case of suspicious tracer uptake. The results of serum thyroglobulin, ultrasonography of the neck, 131I whole-body scintigraphy, chest radiograph, transmission CT or MRI, and bone scintigraphy were also available.

RESULTS: A group of 68 patients without thyroid remnants who were tumor free and had no history of metastases or tumor recurrence showed a negative 99mTc-tetrofosmin whole-body scan. Another 24 patients (papillary carcinoma pT1NOMO) were also in complete remission, but had sonographically proven remnants (echonormal). Sixteen of them (67%) exhibited 99mTc-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 histopathology after reoperation or by cytology after fine-needle aspiration where tetrofosmin scintigraphy clearly revealed relapse of malignancy in all cases. A total of 17 patients had distant metastases (11 pulmonary, 3 bone, 2 bone and pulmonary, 1 bone and soft tissue) discovered by different modalities, resulting in 44 lesions to be evaluated. Of the 23 radioiodine negative metastases, 17 were detected by tetrofosmin (74%), whereas all 21 radioiodine accumulating lesions also showed tetrofosmin positive scans. The overall sensitivity of 99mTc-tetrofosmin in detecting distant metastatic lesions was 86%. Four additional cases with radioiodine-negative disseminated lung metastases showed diffuse pulmonary tetrofosmin uptake.

CONCLUSION: Technetium-99m-tetrofosmin is a promising tracer to detect malignant recurrence and distant metastases in the follow-up of DTC without the necessity of thyroid hormone withdrawal.