BACKGROUND: The ATA risk stratification system has evolved from the 2015 framework toward a more composite nodal risk assessment in the 2025 update. Whether low-volume lateral neck disease remains clinically meaningful is uncertain. We evaluated the prognostic significance of N1b versus N1a disease in papillary thyroid carcinoma (PTC) with ≤5 metastatic lymph nodes. MATERIALS AND METHODS: We identified 11,878 patients with PTC and N1a or N1b disease with ≤5 metastatic lymph nodes from the SEER database (2000-2022). One-to-one propensity score matching was performed. OS and CSS were assessed using Kaplan-Meier analysis, and CSD and OCD using cumulative incidence functions and Fine-Gray models. RESULTS: Among eligible patients, 9,392 had N1a disease and 2,486 had N1b disease. After matching, 2,467 patients remained in each group. N1b was associated with significantly worse OS, CSS, and CSD in both unmatched and matched cohorts. In the matched cohort, 5-year CSD increased from 1.5% to 2.8%. On multivariable Fine-Gray analysis, N1b remained independently associated with higher CSD risk (SHR, 2.52; 95% CI, 1.85-3.43; P 2 cm, and older age. CONCLUSION: Among patients with PTC and ≤5 metastatic lymph nodes, N1b retains independent adverse prognostic significance despite low nodal burden. Low-volume nodal disease should not be considered uniformly low risk when lateral neck involvement is present, particularly in patients with positive ETE, tumor diameter >2 cm, or older age.
Wang et al. (Sat,) studied this question.