Clinical Role of Pre-ablation Stimulated Thyroglobulin and Thyroid-Stimulating Hormone Ratio for Radioactive Iodine Treatment in Adults with Papillary Thyroid Cancer

Objective

This investigation assesses the predictive utility of the pre-ablation stimulated thyroglobulin to thyroid-stimulating hormone ratio (sTg/TSH) and examines the other factors affecting the efficacy of radioactive iodine (RAI) therapy in adult patients with papillary thyroid cancer (PTC).

Methods

We performed a retrospective review of clinical and pathological data from 1071 patients who received a total thyroidectomy followed by RAI therapy. The study included 576 of these patients. Participants were separated into two groups according to their reaction to RAI therapy: excellent response (ER) and non-ER (NER). The factors that contribute to NER were found using univariate and multivariate binary logistic regression analyses. The predictive importance of the sTg and sTg/TSH ratio was discovered by analyzing receiver operating characteristic (ROC) curves and setting diagnostic criteria. Decision curve analysis (DCA) was used to assess the practical implications of these findings.

Results

Among the 576 patients assessed, 60.07% (346 individuals) demonstrated an ER to RAI treatment. Independent predictors of a NER identified through both univariate and multivariate logistic regression analyses included multifocality (odds ratio [OR] = 2.16, 95% confidence interval [CI]: 1.28–3.67, P = 0.004), having more than ten positive lymph nodes (PLN) (OR = 3.78, 95% CI: 1.68–8.54, P = 0.001), presence of distant metastases (OR = 19.22, 95% CI: 2.09–176.93, P = 0.009), elevated stimulated thyroglobulin (sTg) levels (OR = 1.04, 95% CI: 1.00–1.07, P = 0.025), and a higher sTg/TSH ratio (OR = 2.48, 95% CI: 1.80–3.41, P < 0.001). Receiver operating characteristic (ROC) curve analysis established diagnostic thresholds for predicting NER at an sTg level of 7.255 ng/ml (area under the curve [AUC] = 0.893) and an sTg/TSH ratio of 0.127 (AUC = 0.889), both demonstrating robust sensitivity and specificity. Smooth curve fitting illustrated a progressive increase in the risk of NER with rising levels of the sTg/TSH ratio. DCA confirmed the substantial clinical net benefit of these predictors in forecasting NER outcomes.

Conclusions

The sTg/TSH ratio is confirmed as a reliable diagnostic marker for predicting the response to primary RAI treatment in PTC. Moreover, active postoperative follow-up and surveillance are essential for patients with multifocality, PLN >10, sTg >7.255 ng/ml, and sTg/TSH ratio >0.127.