Extent of lymphadenectomy and prognosis in N1b papillary thyroid cancer: A multicenter retrospective cohort study

The optimum extent of neck lymphadenectomy on disease prognosis is unclear in papillary thyroid cancer with laterocervical lymph node metastasis (N1b), despite the need for such data to help guide practice. This study aims to assess the independent impact of the number of examined lymph nodes on clinical outcomes in N1b papillary thyroid cancer patients.

In this cohort study, patients diagnosed with unilateral N1b papillary thyroid cancer who underwent total thyroidectomy with therapeutic lymph node dissection of the central and lateral compartments at 5 tertiary care hospitals in southwestern China from May 2008 through May 2023 were retrospectively analyzed. Univariate and multivariable-adjusted Cox proportional hazards models were constructed to evaluate the association between the number of examined lymph nodes and clinical outcomes. Restricted cubic spline functions were employed to model the nonlinear association between the number of examined lymph nodes and persistent and recurrent disease risk.

Overall, 2,695 patients were included (median [range] age, 38 [18-79] years; 791 men [29.4%]). An increasing number of examined lymph nodes was associated with reduced risk of persistent and recurrent diseases, plateauing at 30 examined lymph nodes (hazard ratio, 0.97; 95% confidence interval, 0.95-0.98; P < .001) in the whole cohort. In T stage-specific subgroup analysis, the T2-T4 subgroup with 31 examined lymph nodes had the most striking prognosis improvements. A linear trend for superior prognosis based on increasing number of examined lymph nodes was found in the T1 subgroup.

This large cohort study indicated that an increasing number of examined lymph nodes in initial surgery is associated with better clinical outcomes for N1b papillary thyroid cancer patients.