Influencing Factors of Urinary Iodine Concentration Before and After Radioiodine Therapy for Differentiated Thyroid Cancer: An Initial Exploration of the Relationship With Therapeutic Efficacy.

Objective: To investigate the impact of urinary iodine concentration (UIC) and post-stimulatory thyroglobulin (ps-Tg) levels on the therapeutic efficacy of differentiated thyroid cancer (DTC) patients after initial radioiodine therapy, and to analyze the validity of these indicators as prognostic factors.

Methods: A total of 213 DTC patients received initial radioiodine therapy from June 2022 to September 2023. Demographic data and UIC were collected before and after therapy. Thyrotropin, thyroglobulin (Tg), and thyroglobulin antibody levels were assessed. Iodine uptake rate was measured, and therapeutic efficacy was evaluated 6 months post-therapy. Statistical tests were used for data comparison, and logistic regression analysis for response factors.

Results: Post-therapy UIC and pre-post UIC difference were significantly correlated with Tg levels but not with reaching excellent response (ER) indicated by suppression of Tg levels below 0.2 ug/L. Ps-Tg levels related to therapeutic efficacy, while UIC did not correlate with outcomes. ROC curve analysis found optimal ps-Tg cut-off points for the low-intermediate and high-risk groups classified by primary tumor size, invasion, metastasis, and pathological type.

Conclusion: Post-treatment UIC and pre-post UIC difference correlate with ps-Tg levels. Ps-Tg levels are an associated factor for DTC, but UIC changes, despite correlation with ps-Tg, are not significantly related to outcomes and cannot be used as a prognostic factor.