Prognostic impact of lymph node characteristics after therapeutic neck dissection for classic N1 papillary thyroid cancer

BACKGROUND: The impact of lymph node characteristics on mortality and recurrence remains controversial. This study evaluated the prognostic impact of lymph node characteristics in a large, homogenous cohort of patients with therapeutic neck dissection for clinically N1 classic papillary thyroid cancer (PTC). METHODS: All consecutive adult patients with therapeutic central and lateral neck dissection for PTC at a French referral centre were prospectively enrolled from January 2000 until June 2021. The primary outcome was the impact of lymph node characteristics in predicting a disease event (persistence or recurrence), using univariable and multivariable logistic regression modelling. RESULTS: A total of 462 patients were included. Lymph node capsular rupture was seen in 260 patients (56.3 per cent). Median maximum lymph node size was 15 (i.q.r. 9–23) mm. The median central, lateral, and total lymph node ratio (LNR) was 0.50 (i.q.r. 0.22–0.75), 0.15 (i.q.r. 0.07–0.29), and 0.26 (i.q.r. 0.14–0.41), respectively. After a median follow-up of 93 (i.q.r. 50–149) months, 182 (39.4 per cent) patients had a disease event. After multivariable analysis, the number of harvested lymph node >35 (OR 2.33 (95 per cent c.i. 1.10–4.95)), presence of lymph node capsular rupture (OR 1.92 (1.17–3.14)), and total LNR >0.20 (OR 2.37 (1.08–5.19)) and >0.40 (OR 4.92 (1.61–15.03)) predicted a disease event. An LNR of 0.20 predicted a disease event with a sensitivity of 80.8 per cent and a specificity of 50.4 per cent. CONCLUSION: Disease persistence or recurrence after thyroidectomy with therapeutic neck dissection for classic PTC with preoperative nodal disease appears to depend on number of harvested lymph node, presence of lymph node capsular rupture, and total LNR.