# Prognostic value of preablative stimulated thyroglobulin and its decline after 131I therapy in differentiated thyroid cancer

## TL;DR

This study shows that thyroglobulin levels before and after radioactive treatment can predict outcomes in thyroid cancer patients.

## Contribution

The study identifies pre-131I thyroglobulin levels and their decline as independent predictors of treatment response in thyroid cancer.

## Key findings

- Lower pre-131I thyroglobulin levels predict better clinical outcomes in thyroid cancer patients.
- A greater decline in thyroglobulin after 131I therapy is associated with more favorable treatment responses.
- A prognostic nomogram was developed to help clinicians make treatment decisions for thyroid cancer patients.

## Abstract

The incidence of differentiated thyroid cancer (DTC) has been increasing, highlighting the need for reliable predictors of treatment response. This study aimed to assess the prognostic value of stimulated thyroglobulin (sTg) levels before and after the first 131I treatment in DTC patients without distant metastases.

Sixty patients were classified into excellent response (ER) and non-excellent response (NER) groups based on a comprehensive evaluation of imaging findings, sTg, suppressed Tg and other parameters. Clinical and pathological variables were analyzed using univariate and multivariate logistic regression. Receiver operating characteristic (ROC) curve analysis was used to determine optimal cut-off values for pre-131I sTg levels and for the rate of sTg decline after the first 131I therapy.

Both pre-131I sTg level (OR: 3.010, 95% CI: 1.004–9.029, p = 0.049) and the rate of sTg decline (OR: 0.756, 95% CI: 0.590–0.968, p = 0.026) were identified as independent predictors of clinical outcomes. The optimal threshold for pre-131I sTg was 14.55 μg/L (sensitivity: 95.0%, specificity: 67.5%, AUC: 0.804), and for the rate of sTg decline, 44.75% (sensitivity: 70.0%, specificity: 97.5%, AUC: 0.889). A prognostic nomogram was developed incorporating sex, age, pre- and post-131I sTg levels, T and N stages, tumor size, and thyroiditis.

Lower pre-131I sTg levels and/or a greater rate of sTg decline after the first 131I treatment are associated with more favorable clinical outcomes. The proposed nomogram may assist clinicians in optimizing treatment decisions and stratifying follow-up strategies for patients with DTC.