Sufficiency of a Single Negative Thyroglobulin Standard for Judging the Success of Ablation in Low- and Intermediate-risk Differentiated Thyroid Cancer: A Retrospective Study

Background: We investigated how reduced successful ablation criteria may be used to evaluate radioiodine remnant ablation in patients with low- and intermediate-differentiated thyroid carcinoma (DTC). Methods: Overall, 254 low- and intermediate-risk patients with DTC were categorized into three groups (positive, weak, positive, and negative) on the basis of a visual study of thyroid imaging performed before postoperative iodine treatment. Semi-quantitative analysis parameters were incorporated into the positive Tc-99m pertechnetate scanning to further examine the clinical use of thyroid imaging. We investigated the value of successful judgment criteria and the influencing factors of radioiodine ablation. At the same time, the predictive value of thyroglobulin (Tg) for radioiodine treatment and the overall clinical efficacy were assessed. Results: A total of 250 (98.43%) patients were identified as having functional thyroid tissue residue on the Rx-whole-body scan, and 137 (53.94%) patients had positive Tc-99m pertechnetate scans using semi-quantitative analysis. The single Tg standard could not substitute the double standard (χ²c=22.042, p<0.001) for patients with residual thyroid weight by a semiquantitative analysis. However, the semi-quantitative analysis revealed no association between 99mTcO4−thyroid scan and ablation treatment using semi-quantitative analysis; only preablation sTg levels were related with success in the multivariate logistic regression analysis, with a cut-off value of 2.88 ng/mL. The pre-ablation stimulated Tg level was also the primary factor of satisfactory response following follow-up with an optimal cut-off of 6.506 ng/mL. Conclusion: Even in low- and intermediate-risk patients with DTC, a single negative Tg standard also requires receiving some restrictions in the evaluation of ablation success and is inadequate. Conventional 99mTcO4 thyroid imaging combined with a quantitative analysis program can improve the clinical practice of single negative Tg standard.