Effect of Radioactive Iodine Therapy on Cancer-Specific Survival of Papillary Thyroid Carcinoma With T4aM0 Stage.

[CONTEXT] Papillary thyroid carcinoma (PTC) with T4aM0 stage, which involves extrathyroidal extension without distant metastasis, presents challenges in treatment management. While radioactive iodine (RAI) therapy has been shown to benefit certain high-risk thyroid cancer patients, its effect on cancer-specific survival (CSS) in T4aM0 PTC patients remains unclear.

[OBJECTIVE] We aim to evaluate the impact of RAI therapy on CSS in T4aM0 PTC patients following total thyroidectomy.

[METHODS] 1938 PTC patients with T4aM0 stage who underwent total thyroidectomy in the SEER database were identified. Clinical-pathological and CSS data were systematically collected. Patients were stratified into the RAI-treated group and the non-RAI-treated group. Propensity score matching (PSM) was implemented with 1:1 nearest-neighbour matching to balance baseline covariates. Intergroup comparisons of demographic and clinical characteristics were performed in the entire cohort and PSM cohort. Subset analyses were conducted to indicate the effect of RAI therapy on CSS in different subgroups. Cox proportional hazards regression models were employed to evaluate CSS outcomes.

[RESULTS] After PSM, 472 pairs of patients were included in the analysis. In both the entire cohort and the PSM cohort, no significant difference in CSS was observed between RAI-treated and non-RAI-treated patients (HR = 0.797, 95% CI: 0.540-1.175, p = 0.252; HR = 0.709, 95% CI: 0.437-1.151, p = 0.709). Subgroup analysis also showed no survival benefit of RAI across various clinical characteristics.

[CONCLUSION] RAI therapy does not significantly improve cancer-specific survival in T4aM0 PTC patients after total thyroidectomy. These findings suggest that RAI may not be necessary for this subgroup, advocating for more individualised treatment approaches.