Not the Number but the Location of Lymph Nodes Matters for Recurrence Rate and Disease-Free Survival in Patients with Differentiated Thyroid Cancer

Several Japanese studies have focused on identifying prognostic factors in patients with positive lymph nodes to predict recurrence rate and disease-free survival (DFS). However, different treatment protocol is followed in Japan compared with the European and American approach. This study was designed to investigate whether the number and/or location of lymph nodes predicts prognosis in patients with DTC treated with total thyroidectomy, lymph node dissection, and postoperative radioactive iodine ablation. All 402 patients who were treated at the Department of Nuclear Medicine between 1998 and 2010 for DTC were reviewed. Patients were treated with (near) total thyroidectomy, lymph node dissection on indication, and postoperative I-131 ablation. Median follow-up was 49 (range, 10-240) months. Outcome measures were recurrence rate, disease-free survival, and mean time to recurrence. Ninety-seven patients had proven lymph node metastases. Recurrence rate was significantly higher in patients with positive lymph nodes in the lateral compartment vs. patients with lymph node metastasis in the central compartment (60 vs. 30%, = 0.007). Disease-free survival and mean time to recurrence also were significantly shorter (30 vs. 52 months, = 0.035 and 7 vs. 44 months, = 0.004, respectively). The number of lymph nodes and extranodal growth were not significantly associated with the outcome measures used. The location of positive lymph nodes was significantly correlated with the risk of recurrence and a shorter DFS. Hence, the TNM criteria are useful in subdividing patients based on risk of recurrence and DFS.