Prospective outcomes of selective lymph node dissection for papillary thyroid carcinoma based on preoperative ultrasonography.

BACKGROUND: Although many patients with papillary thyroid carcinoma (PTC) display associated cervical lymph node metastases (LNM), the optimal extent of lymph node dissection (LND) remains a matter of debate. Since 1993, we have performed cervical LND based on the preoperative suspicion of LNM by ultrasonography (US). We prospectively analyzed the outcomes of our "selective" LND to determine when prophylactic lateral neck dissection is advisable.

METHODS: Prospective analysis was conducted for 361 consecutive patients with PTC who received initial surgery between 1993 and 2001. Mean duration of follow-up was 8.1 years. Dissection of the central compartment only was performed for patients with LNM in the central zone only and for patients with no LNM detected by US (Group A). Modified radical lateral neck dissection (MND; combined with central compartment dissection) was performed for patients diagnosed with lateral neck LNM (Group B).

RESULTS: Pathological LNM was found in 136 of 231 patients in Group A (59%). As for the accuracy of US diagnosis, positive predictive value was 82%. Nodal recurrences, occurring all in the lateral cervical region associated with one case of contralateral paratracheal region, was seen in 18 patients (8%) and 10-year nodal disease-free survival was 91%. Univariate analysis revealed true positive diagnosis by US, large primary tumor (> or = 4 cm), primary tumor located in the upper part of the thyroid lobe, presence of distant metastasis, extrathyroidal invasion of the primary tumor, and a poorly differentiated component of the primary tumor as significant risk factors for nodal recurrence. Among the risk factors that could be diagnosed preoperatively, distant metastasis (risk ratio, 46; p = 0.01) and large primary tumor (risk ratio, 3.6; p = 0.03) were the most important factors under multivariate analysis. Of the other 130 patients in Group B, only 3 patients had no pathological LNM (positive predictive value, 98%). Twenty-six patients (20%) developed nodal recurrence, with a 10-year nodal disease-free survival of 76%. Age (50 years or older), large nodal metastasis (> or = 3 cm), extrathyroidal invasion, and higher serum thyroglobulin level (> or =320 ng/ml) represented significant factors for nodal recurrence.

CONCLUSIONS: When preoperative US shows no LNM or indicates only LNM in the central compartment, dissection of the central compartment alone offers a sufficient alternative to routine prophylactic MND. However, patients with PTC demonstrating large primary tumor and/or distant metastasis were high-risk for recurrence in the lateral cervical compartment. We recommend prophylactic MND to reduce nodal recurrence for those patients.