The effect of total thyroidectomy and radioactive iodine on longterm survival in unilateral T3/T4 follicular thyroid carcinoma: insights from a propensity-matched retrospective analysis

Background: Follicular thyroid carcinoma (FTC) is the second most common thyroid malignancy and is particularly aggressive in advanced stages such as T3 and T4. This retrospective study aimed to evaluate the long-term survival outcomes of total thyroidectomy (TT) and radioactive iodine therapy (RAIT) in unilateral T3 or T4 FTC using propensity score-matched analysis. Methods: Utilizing the Surveillance, Epidemiology, and End Results (SEER) database, we identified patients diagnosed with T3 or T4 FTC and categorized them into two cohorts, namely those who were treated with TT and those who were not (non-TT). The non-TT group was further analyzed to determine the impact of RAIT on survival. Propensity score matching (PSM) was applied to adjust for confounding variables. Survival analysis, including Kaplan-Meier survival curves and landmark analysis, evaluated the effects on overall survival (OS) and cancer-specific survival (CSS). Results: A total of 2,957 patients were included, with 2,271 (76.8%) undergoing TT and 686 (23.2%) receiving alternative treatments. Before and after PSM, there were no significant differences in OS and CSS between the two groups. Post-PSM landmark analysis revealed that beyond 90 months, the TT group had superior CSS compared with the non-TT group (P=0.06). Cox multivariate regression identified follicular adenocarcinoma trabecular [hazard ratio (HR) =4.7041; 95% confidence interval (CI): 1.1218-19.727] and minimally invasive follicular carcinoma (HR =2.0202; 95% CI: 1.2140-3.362) as independent risk factors affecting prognosis. In the second part of the study, 671 patients were analyzed, namely 197 (29.4%) who received RAIT and 474 (70.6%) who did not. Landmark analysis indicated that after 30 months, the RAIT group had superior CSS compared with the non-RAIT group (P<0.05). Conclusions: TT does not improve the survival rates of patients with stage T3/T4 FTC. For those patients who have not undergone TT, RAIT proves beneficial for CSS; however, further in-depth studies are required.