The Effectiveness of Prophylactic Modified Neck Dissection for Reducing the Development of Lymph Node Recurrence of Papillary Thyroid Carcinoma

AIM: The most frequent recurrence site of papillary thyroid carcinoma (PTC) is the cervical lymph nodes. The introduction of an electric linear probe for use with ultrasonography in 1996 improved preoperative lateral neck evaluations. Before 2006, however, our hospital routinely performed prophylactic modified neck dissection (p-MND) for N0 or N1a PTCs >1 cm to prevent node recurrence. In 2006, we changed our policy and the indications for p-MND to PTCs >3 cm and/or with significant extrathyroid extension. Here, we retrospectively compared lymph node recurrence-free survival between PTCs with/without p-MND. METHODS: We examined the cases of N0 or N1 and M0 PTC patients who underwent initial surgery in 1992–2012. To compare lymph node recurrence-free survival between patients who did/did not undergo p-MND, we divided these patients into three groups (excluding those whose surgery was in 2006): the 2045 patients whose surgery was performed in 1992–1996 (Group 1), the 2989 with surgery between 1997 (post-introduction of ultrasound electric linear probes) and 2005 (Group 2), and the 5332 operated on in 2007–2012 (Group 3). RESULTS: The p-MND performance rate of Group 3 (9%) was much lower than that of Group 1 (80%), but the lymph node recurrence-free survival of the former was significantly better, probably due to differences in clinical features and neck evaluations by ultrasound between the two groups. Our analysis of the patients aged <75 years with 1.1–4-cm PTCs in Groups 2 and 3 showed that p-MND did not improve lymph node recurrence-free survival. p-MND did significantly improve lymph node recurrence-free survival for the extrathyroid extension-positive 3.1–4-cm PTCs, but not for the other subsets. CONCLUSIONS: Abolishing routine p-MND for PTCs in 2006 did not decrease lymph node recurrence-free survival, probably due to improved ultrasound preoperative neck evaluations and clinical feature changes. Selective p-MND for high-risk cases improved lymph node recurrence-free survival.