Are Total Thyroidectomy and Adjuvant Radioactive Iodine Treatment Required in All Patients with N1b Intermediate-High Risk Papillary Thyroid Carcinoma?

[BACKGROUND] The optimal extent of surgery and the role of radioactive iodine (RAI) in patients with papillary thyroid carcinoma (PTC) with lateral neck metastasis (cN1b) remain controversial. We aimed to evaluate the oncologic outcomes of lobectomy with lateral neck dissection, total thyroidectomy with lateral neck dissection, and total thyroidectomy with lateral neck dissection followed by adjuvant RAI in patients with intermediate-risk cN1b PTC.

[METHODS] In this multicenter retrospective cohort study, we included patients with cT1-3N1bM0 PTC who underwent thyroidectomy with therapeutic lateral neck dissection between 2010 and 2022. Recurrence-free survival (RFS) and disease-specific survival (DSS) were compared across three treatment groups using Kaplan-Meier. Multivariable cox proportional hazards models were also used to identify independent risk factors for recurrence.

[RESULTS] We included 593 patients (60.6% female; median age, 58.0 years) who had a median follow-up duration of 71.5 months. We observed no significant differences in RFS ( = 0.19) or DSS ( = 0.40) among the treatment groups of lobectomy, total thyroidectomy, and total thyroidectomy with RAI. Although the total thyroidectomy with RAI group showed a trend toward worse RFS, this was not statistically significant ( = 0.19). In multivariable analysis, older age (hazard ratio [HR] 1.024 per year, confidence interval [CI] 1.007-1.041, = 0.006), larger primary tumor size (HR 1.026 per mm, CI 1.012-1.041, < 0.001), larger metastatic lymph node size (HR 1.020 per mm, CI 1.003-1.036, = 0.017), and extranodal extension (HR 1.741, CI 1.046-2.898, = 0.033) were independently associated with shorter RFS.

[CONCLUSIONS] RAI may improve RFS in selected patients with extensive nodal disease, but its routine use in all cN1b PTC cases may be unnecessary. Lobectomy or total thyroidectomy without RAI could be appropriate options in lower risk cN1b patients. Further studies are warranted to refine treatment strategies in intermediate-risk cN1b PTC.