Preablative Stimulated Thyroglobulin and Thyroglobulin Reduction Index as Decision-Making Markers for Second Radioactive Iodine Therapy in Patients with Structural Incomplete Response

Abstract

Purpose

The aim of this study was to evaluate the value of preablative stimulated thyroglobulin (presTg) and thyroglobulin reduction index (TRI) to predict the different responses to second radioactive iodine (RAI) therapy in differentiated thyroid cancer (DTC) patients with structural incomplete response (SIR).

Patients and Methods

A single-center retrospective study analyzed the different clinical outcomes after second RAI therapy in 206 patients with SIR. PresTg1 and presTg2 were measured before first and second RAI management and TRI was the reduction index of presTg1 and presTg2. Cut-off values of presTg and TRI were obtained using receiver operating characteristic analysis. The univariate logistic regression analysis was performed to confirm these parameters as prognostic factors to predict different responses to second RAI therapy.

Results

Only ATA risk stratification, the post-therapy whole-body scanning (Rx-WBS) findings, presTg1, presTg2, TRI, were different in patients with SIR. After second RAI therapy, 28.2% (58/206) of patients with SIR initially were reclassified as excellent response (ER). PresTg1 <6.6 ng/mL, presTg2 <1.2ng/mL, and TRI >74.2% were excellent indications to predict ER from non-ER after second RAI treatment. PresTg1 >14.9 ng/mL, presTg2 >1.8ng/mL and TRI <66.5% were well markers to predict poor outcome (SIR). High risk and distant metastases could still be considered as risk factors.

Conclusion

DTC patients with SIR could benefit through second RAI treatment. PresTg before each RAI therapy and TRI could be considered as effective decision-making markers for second RAI therapy and as predictive indications for clinical outcomes.

Keywords:

• structural incomplete response
• radioactive iodine therapy
• preablative stimulated thyroglobulin
• thyroglobulin reduction index
• differentiated thyroid carcinoma

Acknowledgments

This work was supported by the Jinan clinical medical science and technology innovation plan (Grant No: 202019194). Co-first author: Lihua Wang and Canhua Yun.

Abbreviations

AJCC, American Joint Committee on Cancer; ATA, American Thyroid Association; AUC, area under the curve; BIR, biochemical incomplete response; CI, confidence interval; DTC, differentiated thyroid carcinoma/cancer; DM, distant metastases; ER, excellent response; ETE, extra-thyroid extension; IDR, indeterminate response; LNM, lymph node metastasis; PresTg, preablative stimulated thyroglobulin; PTC, papillary thyroid carcinoma/cancer; RAI, radioactive iodine; ROC, receiver operating characteristic; Rx-WBS, Post-therapy whole-body scanning; SIR, structural incomplete response; TgAb, anti-thyroglobulin antibody; THW, thyroid hormone withdrawal; TNM, tumor node metastasis; TRI, thyroglobulin reduction index; TSH, thyroid-stimulating hormone; TT, total thyroidectomy.

Ethics Statement

The patient data extracted from the clinical electronic medical record system were identified such that all private information was not included. The Institutional Review Board (IRB) of Second Hospital of Shandong University approved the use of records and allowed us to not obtain written consent from each patient (KYLL-2018[LW]013). All procedures complied with the Declaration of Helsinki for research involving human subjects.

Disclosure

The authors declare that they have no competing interests.