Predicting thyroid cancer ablation success: Pre-ablative 99mTc-Pertechnetate and post-ablative 131I scan comparison

Introduction

The purpose of this study was to evaluate the relationship between pre-ablative ^99mTc-pertechnetate scintigraphy, and therapeutic iodine-131 (¹³¹I) whole-body scan (TxWBS), with ablation status and to investigate the possible predictive factors for successful ablation in differentiated thyroid carcinoma (DTC) patients.

Materials and methods

A total of 330 DTC patients underwent ^99mTc-pertechnetate scintigraphy after thyroidectomy. Uptake values were determined using the region-of-interest technique. All patients had neck ultrasonography and TxWBS. Both scintigraphic scans were interpreted visually and qualitatively. The ablation status was evaluated with a diagnostic ¹³¹I whole-body scan.

Results

The success rate for residual thyroid ablation was 88.8%. The sensitivity, specificity, accuracy, PPV, and NPV of ^99mTc-Pertechnetate scintigraphy were 82.4%, 87.5%, 82.7%, 99.2%, and 20.2%, respectively. Pre-ablative TG values and ^99mTc uptake (%) were significantly lower in successfully ablated patients. The ^99mTc uptake was determined as a significant predictive factor for ablation success (P = 0.000). The optimal ^99mTc uptake cut-off value of 0.75% was demonstrated for successful ablation. There were significant positive correlations between the visual and the calculated uptake (%) of residual tissues on both scintigraphic scans, Considering the number of remnant tissue foci, significant positive correlations were found between ^99mTc-Pertechnetate scintigraphy, TxWBS, and USG.

Conclusion

Pre-ablative ^99mTc-Pertechnetate uptake (%) value of the remnant tissue can predict the ablation status in DTC patients. ^99mTc-Pertechnetate scintigraphy, which is an easily applicable and accessible imaging method, has maintained its place in the postoperative and pre-ablative period in DTC patients over the years and has not lost any of its value.