Prediction of the success of thyroid remnant ablation using preablative Tc-99m pertechnetate scintigraphy and postablative dual I-131 scintigraphy

Abstract

ObjectiveThe aim of this study was to predict the success of I-131 ablation using preablative Tc-99m pertechnetate salivary scintigraphy and a postablative dual I-131 scan in differentiated thyroid cancer (DTC).Patients and methodsA total of 168 DTC patients who underwent I-131 ablation with preablative salivary scintigraphy and a postablative dual (early and delayed) I-131 scan were enrolled. For salivary scintigraphy, the thyroid remnant uptake was visually assessed. For the dual I-131 scan, the thyroid remnant to background uptake ratios (TBRs) on early and delayed scans were measured and the percentage change in TBR (TBR) was calculated.ResultsThyroid remnant uptake was seen in 69 (41%) patients on salivary scintigraphy and in 162 (96%) patients on the dual I-131 scan. The success rate of ablation was higher in patients with negative remnant uptake on salivary scintigraphy (86%) than in patients with positive remnant uptake (58%, P=0.0001). The success rate of ablation was 100% in patients with no remnant uptake on both salivary scintigraphy and the dual I-131 scan. The success rate of ablation was higher in patients with TBR 0 or more than in patients with TBR less than 0, irrespective of remnant uptake on salivary scintigraphy (91 vs. 70%, P=0.03, for patients without remnant uptake on salivary scintigraphy; 74 vs. 48%, P=0.05, for patients with remnant uptake on salivary scintigraphy).ConclusionThe success of thyroid remnant ablation in DTC can be predicted by the presence of remnant uptake on preablative Tc-99m pertechnetate scintigraphy and change in remnant uptake on the postablative dual I-131 scan.