A quantitative study about thyroid stunning after diagnostic whole-body scanning with 74 MBq 131I in patients with...

The aim of this paper was to explore by a quantitative method whether a 74 MBq 131I scanning activity produces a stunning effect in patients with differentiated thyroid carcinoma (DTC).

We included 70 patients with DTC who had their first radioiodine treatment for ablation of thyroid remnants and/or metastases. All the patients received 1850~7400 MBq 131I. Before ablation, 34 patients (group A) performed a diagnostic scan (Dscan) 24 hours after the administration of 74 MBq 131I; 36 patients (group B) received 131I therapy without a previous Dscan. A therapeutic scan (Tscan) was performed after the ablation. The fractional concentrations of 131I in remnants or functional metastases were quantified on Dscan and Tscan, and were expressed as Dx and Tx respectively. The level of significance was set at 0.05.

For group A, 67 foci were found both on Dscan and Tscan, the mean Dx and Tx was 26.13±37.98 and 7.46±10.63 (P=0.000), respectively. For group B, 70 foci were found on Tscan, the mean Tx was 15.23±17.23, which was higher than group A significantly (P=0.002).

74 MBq 131I for diagnostic scan can decrease the uptake of 131I by thyroid remnants or metastases, the thyroid stunning exists.