Postoperative routine radioiodine (RAI) treatment is currently debated for patients with low-risk differentiated thyroid carcinoma (DTC) patients. If performed, a low ¹³¹I activity (i.e., 1 to 2 GBq) is recommended with the aim to ablate thyroid remnant and facilitate subsequent follow-up by thyroglobulin measurement. The purpose of this study was to evaluate the relationship between postsurgical technetium-99m (^99mTc)-pertechnetate scintigraphy and the rate of successful remnant ablation after low activity radioiodine ablation in patients with DTC.

Enrolled were 193 patients with low risk DTC who underwent total thyroidectomy and RAI ablation with a fixed 1.1 GBq activity of ¹³¹I. ^99mTc-pertechnetate scans were done and thyrotropin stimulated thyroglobulin (sTg) levels measured just before ablation. Ablation effectiveness was assessed 6 to 12 months later by sTg measurement, neck ultrasound and diagnostic whole body scan.

A negative ^99mTc-perthecnetate scans was the best predictor of successful ablation (P<0.001) followed by preablative sTg levels <0.8 ng/mL (P=0.008) and ^99mTc-pertechnetate uptake rate values <0.9% (P=0.065). Neither sex nor age of the patient at the time of ablation or tumor histology and size showed a significant association with the rate of successful ablation.

The ^99mTc-pertechnetate scintigraphy is a simple and feasible tool to predict effectiveness of low activity ¹³¹I thyroid to ablate thyroid remnants in patients with DTC.