Utility of Stimulated Thyroglobulin in Reclassifying Low Risk Thyroid Cancer Patients' Following Thyroidectomy and Radioactive Iodine Ablation: A 7-Year Prospective Trial

Basal or stimulated thyroglobulin in evaluating response to treatment in papillary thyroid carcinoma? A retrospective cohort study

OBJECTIVE

It is not clear whether response to initial treatment in papillary thyroid carcinoma (PTC) patients is best evaluated by measuring thyroglobulin (Tg) in the presence of levothyroxine (BTg) or when stimulated by elevated TSH (STg). The aim of this study was to evaluate whether response to therapy 1 year after initial treatment changes with the use of STg in relation to BTg in PTC patients treated with total thyroidectomy (TT) and radioiodine (131I), and, if observed, to assess which response is better associated with clinical course.

SUBJECTS AND METHODS

This is a retrospective study of 148 PTC patients submitted to TT and 131I. We analyzed the response to therapy (excellent, biochemical incomplete, or indeterminate) at 1 year after initial treatment, using BTg or STg, and compared which method was better associated with "excellent response at final evaluation."

RESULTS

Twenty-eight patients (20.4%) presented change in response to therapy, with 17 of these (60.7%) presenting a worse response. Response using STg was 1.6 times better associated with proposed outcome [odds ratio (OR) = 4.61; confidence interval 95% (IC95%): 2.13-9.98] than with BTg (OR = 2.84; IC95%: 1.33-6.06).

CONCLUSION

Response to therapy at 1 year using STg was altered in approximately 20% of cases and therefore proved to be a better predictor of excellent response in the last evaluation.

Comparison of Prognostic Value Between Stimulated and Nonstimulated Thyroglobulins in Differentiated Thyroid Cancer: A Retrospective Study

Purpose

The growing incidence of differentiated thyroid cancer (DTC) demands dependable prognostic factors to guide follow-up and treatment plans. This study investigated the prognostic value of response to therapy (RTT) assessment using TSH stimulated-thyroglobulin (sti-Tg) and nonstimulated-thyroglobulin (nonsti-Tg) and evaluates whether RTT using nonsti-Tg (nonstiRTT) can replace RTT using sti-Tg (stiRTT) in clinical practice to improve patients' quality of life during assessment.

Methods

We enrolled 419 DTC patients who underwent total thyroidectomy, radioactive iodine (RAI) therapy, and Tg assessment. Patients with structural incomplete responses were excluded. Initial RTT assessments based on the 2015 American Thyroid Association guidelines (excellent response; ER, indeterminate response, biochemical incomplete response) were performed 6-24 months after RAI therapy. The second RTT assessments were performed 6-24 months after the first assessment. Statistical analysis for recurrence-free survival (RFS) was done with the log-rank test for stiRTT and nonstiRTT.

Results

Although initial stiRTT and nonstiRTT were significant predictors for RFS (p < 0.0001), stiRTT provided better RFS prediction than nonstiRTT. The RFS analysis of the second RTT assessment demonstrated statistical significance only for stiRTT (p < 0.0001). In 116 patients classified as ER on initial stiRTT, there was no RFS difference between patients classified as ER on either second stiRTT or nonstiRTT.

Conclusion

The prognostic power of stiRTT surpasses that of nonstiRTT in both the initial and second RTT assessment. Nevertheless, among patients classified as ER on initial stiRTT, a second stiRTT may not be required for those classified as ER on the second nonstiRTT.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13139-023-00811-8.

A Retrospective Cohort Study with Validation of Predictors of Differentiated Thyroid Cancer Outcomes

Background: The goal of radioactive iodine (RAI) in differentiated thyroid cancer (DTC) is to treat metastasis and reduce recurrence risk. International guidelines provide broad risk stratification to aid treatment decisions, but a more nuanced approach to individualize care is warranted. We developed a predictive risk model for DTC. Methods: We performed a retrospective multivariable analysis of 899 patients who received RAI after thyroidectomy at a quaternary center in Australia between 2008 and 2016. Collected data included age, gender, histology, stimulated thyroglobulin (sTg), and 8th American Joint Committee Cancer (AJCC) staging. The ATA Modified Initial Risk (ATA) was calculated retrospectively. Recurrence was defined as clinically significant progression requiring either surgical intervention or administration of a second activity of RAI. Synchronous metastasis was defined as distant metastasis (i.e., outside of the neck) that was present at the time of diagnosis on structural imaging or initial post-iodine treatment scan. The features significantly associated with synchronous metastasis or recurrence were employed in the generation of a predictive risk model. A separate cohort of 393 patients who received RAI in 2017-2021 was used for validation. Results: On multivariate analysis, sTg ≥10 μg/L, extrathyroidal extension (ETE) and lymph node involvement predicted recurrence. Independent of ATA, patients with sTg ≥10 μg/L had a shorter disease-free survival (DFS) than those with sTg <10 μg/L (p < 0.001). The ETE stratified by four histological categories was significantly associated with worse DFS (p < 0.001). In a subset of patients, the presence of thyroglobulin antibody (TgAb) did not influence recurrence in patients with sTg <10 μg/L. On multivariate analysis, widespread ETE, sTg ≥10 μg/L, multifocal papillary thyroid cancer and follicular thyroid cancer were positively associated with synchronous metastasis. A predictive risk model was developed to estimate synchronous metastasis/recurrence risk and validated successfully in the second cohort. Conclusions: Our novel predictive risk model modifies and extends ATA stratification by including sTg and ETE, which we found to be independent predictors of both recurrence and synchronous metastasis in DTC.