Assessment of Different Radioiodine Doses for Post-ablation Therapy of Thyroid Remnants: A Systematic Review

Higher adjuvant radioactive iodine therapy dosage helps intermediate-risk papillary thyroid carcinoma patients achieve better therapeutic effect

Objective

This retrospective study aims to evaluate the therapeutic effect of varying dosages of adjuvant radioactive iodine (RAI) therapy on intermediate-risk papillary thyroid carcinoma (PTC) patients.

Methods

This retrospective study involved a total of 427 intermediate-risk PTC patients, out of which 202 received a 3.7GBq dosage of RAI, and 225 received a 5.55GBq dosage. The evaluation involved assessing the therapeutic outcomes, number of treatment cycles, and successful remnant ablation rates in both dose groups, six months post-adjuvant RAI therapy. Univariate and multivariate logistic regression analyses were employed to identify factors linked with excellent response (ER). Following this, prognostic nomograms were constructed to provide a visual representation of the prediction models. Calibration curves, the concordance index (C-index), and the receiver operating characteristic (ROC) curve were employed to evaluate the predictive performance of these nomograms. The Hosmer-Lemeshow test was applied to assess the models' goodness-of-fit. Additionally, the clinical utility of the prognostic nomograms was appraised through decision curve analysis (DCA).

Results

The high-dose (HD) group exhibited significantly higher proportions of ER, single treatment cycles, and successful remnant ablation rates (p<0.05). Being male, receiving a 3.7GBq dose, having an N1b stage, an sTg level ≥10ng/ml, or an sTg/TSH ratio ≥0.11 were independent risk factors for Non-ER. Two prognostic nomograms, "sTg Nomogram" and "sTg/TSH Nomogram", were established. The ranking of factors contributing to ER, in descending order, included the sTg or sTg/TSH ratio, N stage, therapy dosage, sex, and soft tissue invasion. The "sTg/TSH Nomogram" demonstrated a higher C-index compared to the "sTg Nomogram". The calibration curves indicated excellent calibration for both nomograms. DCA demonstrated that the net benefit of the "sTg/TSH Nomogram" was higher than that of the "sTg Nomogram".

Conclusion

Higher initial RAI therapy doses can improve therapeutic efficacy for intermediate-risk PTC patients. The developed nomograms, particularly the "sTg/TSH Nomogram", could assist clinicians in optimal therapeutic decision-making.

Radioactive Iodine in Differentiated Carcinoma of Thyroid: An Overview

Thyroid cancer is the fifth most prevalent cancer in women and the fastest-growing malignancy. Although surgery is still the basis of treatment, internal radiation therapy (Brachytherapy) with radioactive iodine-131, which functions by releasing beta particles with low tissue penetration and causing DNA damage, is also a potential option. The three basic aims of RAI therapy in well-differentiated thyroid tumors are ablation of the remnant, adjuvant therapy, and disease management. Radioactive iodine dose is selected in one of two ways, empiric and dosimetric, which relies on numerous criteria. The dosage for ablation is 30-100 mCi, 30-150 mCi for adjuvant therapy, and 100-200 mCi for treatment. The RAI treatment effectively aids in the treatment to achieve complete removal of the disease and increase survival. The present review intends to emphasize the significance of radioactive iodine in the management of differentiated thyroid cancer and put forward the current breakthroughs in therapy.