Values of (99m)Tc-methoxyisobutylisonitrile imaging after first-time large-dose (131)I therapy in treating differentiated thyroid cancer.

Abstract

ObjectiveThe aim of this study is to investigate the use of 99mTc-methoxyisobutylisonitrile (MIBI) imaging for evaluating the treatment response of differentiated thyroid cancer (DTC) after the first administration of a high dose of 131I.MethodsPatients with DTC who received 131I therapy underwent 99mTc-MIBI imaging after successive increases in the therapeutic dose of 131I, and the serum levels of thyroglobulin (Tg) were measured.ResultsA total of 191 patients were enrolled in the final analysis, including 65 metastases and/or thyroid remnant-positive patients (22 patients with metastases and 43 patients with thyroid remnants). The sensitivity of 99mTc-MIBI imaging for detecting positive cases and thyroid remnants was 56.9% and 39.5%, respectively, which was significantly lower than that of 131I imaging (92.3% and 100%, respectively, P<0.01 for both). The sensitivity of 99mTc-MIBI imaging for detecting metastases was 90.9%, which was slightly higher than that of 131I imaging (77.3%, P>0.05). The Tg levels in the positive group were significantly higher than that in the negative group (P<0.01). In addition, the Tg levels in the 99mTc-MIBI+/131I− group were significantly higher than that in the 131I+/99mTc-MIBI group (P<0.05).ConclusionAfter the first 131I therapy, although 99mTc-MIBI imaging was able to detect the existence of metastatic lesions in patients with DTC better, its assessment for the removal efficiency of thyroid remnants was unsatisfactory. The results of 99mTc-MIBI imaging showed good correlations with the Tg level.