Comparative outcomes of retreatment vs follow-up in DTC patients with intermediate response following initial radioactive iodine therapy: a retrospective cohort study.

BACKGROUND: The optimal management for differentiated thyroid cancer (DTC) patients with an indeterminate response (IDR) to initial radioactive iodine(RAI) therapy remains a clinical dilemma. This study aimed to compare outcomes between active surveillance and RAI retreatment in IDR patients and to identify predictors of persistent non-excellent response (NER). METHODS: This retrospective cohort study included 136 DTC patients classified as IDR 6 months after initial RAI therapy. Patients were categorized into a Retreatment Group (n = 18), who received additional RAI treatment, and a Follow-up Group (n = 118), managed with active surveillance. Treatment response was assessed during follow-up. RESULTS: The rate of excellent response (ER) was significantly higher in the Follow-up Group compared to the Retreatment Group (58.47% vs. 33.33%, P = 0.046). In the Follow-up Group, multivariate analysis identified older age (≥ 45.50 years; OR, 1.07; P < 0.001), lateral cervical lymph node metastasis (N1b; OR, 2.92; P = 0.016), and higher stimulated thyroglobulin (sTg) level at first follow-up (≥ 2.025 ng/mL; OR, 1.31; P < 0.001) as independent predictors of NER. A nomogram incorporating these three factors demonstrated good predictive accuracy, with an area under the curve (AUC) of 0.752, which was confirmed by internal validation (AUC = 0.752). CONCLUSION: For DTC patients with an IDR, active surveillance was associated with a higher rate of ER compared to immediate RAI retreatment. A nomogram based on age, N1b status, and sTg level can effectively stratify the risk of NER, potentially guiding more individualized management decisions for this patient population.