Association of Radioactive Iodine Administration With Outcome Among Patients With Low-Risk Differentiated Thyroid Cancer: A Real-World Data Analysis

Objective: Despite the generally favourable long-term prognosis of low-risk differentiated thyroid cancer (DTC), questions remain about disease-free survival (DFS) after initial treatment, particularly regarding the use of radioactive iodine (RAI). Although there are RCT trial confirming that RAI ablation therapy is not superior to follow-up in terms of the 3-year DFS rate in low-risk thyroid cancer, its longer-term prognosis remains to be established. The objective of this study was to assess the impact of RAI ablation on the presence of structural persistent/recurrent disease in patients with low-risk DTC.

Methods: We retrospectively identified 720 low-risk DTC patients who had undergone total or near-total thyroidectomy (TT) at a tertiary medical centre between January 2008 and July 2018. Propensity scores were calculated using a multivariable logistic regression model that accounted for age, sex, tumour size, neck dissection, multifocality, capsular invasion and lymph node (LN) metastasis. We compared DFS between patients who received RAI and those who did not using log-rank tests and multivariate Cox analyses. Subgroup analyses were also conducted.

Results: Of the total cohort, 180 (25.0%) patients received RAI, while 540 (75.0%) did not before matching. The median follow-up duration was 59.5 months. After matching, the RAI group comprised 135 (39.8%) patients and the non-RAI group comprised 204 (60.2%) patients. In the entire cohort, the 5-year DFS rate was 97.6% for patients receiving RAI compared to 96.8% for those not receiving RAI (p = 0.704). In the matched cohort, the rates were 98.5% and 95.6%, respectively (p = 0.090). Matched multivariate Cox analysis demonstrated that RAI was neither significantly nor independently associated with DFS (hazard ratio [HR] = 0.29; 95% CI 0.06-1.37; p = 0.118). Further subgroup analyses reaffirmed that RAI ablation did not significantly reduce the risk of developing structural persistent/recurrent disease.

Conclusion: Administering RAI ablation following TT did not result in improved DFS for low-risk DTC patients. Our findings suggest that decisions regarding RAI should be made judiciously to avoid overtreatment in this clinical scenario.