Lymph node recurrence in patients with N1b papillary thyroid carcinoma who underwent unilateral therapeutic modified radical neck dissection.

Background: Therapeutic modified radical neck dissection (MND) is a mandatory surgical procedure for patients with papillary thyroid carcinoma (PTC) having clinical lateral node metastasis (N1b). However, N1b PTC is still likely to recur in regional lymph nodes after surgery. We investigated the clinicopathological features predicting recurrence in nodes in previously dissected compartments (ipsilateral lateral compartment or central compartment) and nodes in the contralateral lateral compartment for N1b patients who underwent unilateral therapeutic MND.

Methods: A total of 744 N1b PTC patients who underwent thyroidectomy with unilateral therapeutic MND between 1987 and 2004 were enrolled in the study. The patient ages ranged from 12 to 88 years (average 50.2 years). The average postoperative follow-up period was 113 months.

Results: To date, 87 (12%) and 49 (7%) patients showed recurrence in previously dissected compartments and the contralateral lateral compartment, respectively. On univariate analysis, age >55 years, node metastasis >3 cm, extranodal tumor extension, and extrathyroid extension affected recurrence in previously dissected compartments. Also, the former two were independent predictors on multivariate analysis (P = 0.0170 and <0.0001, respectively). In contrast, only extrathyroid extension and tumor size >4 cm influenced recurrence in the contralateral lateral compartment on univariate analysis. On multivariate analysis, the former was an independent predictor (P = 0.0015), and the latter was of marginal significance (P = 0.0909). To date, 13% of patients having both of these characteristics showed recurrence in the contralateral lateral compartment.

Conclusions: Extremely careful therapeutic MND is required for N1b patients with age >55 years or node metastasis >3 cm because of the likelihood of recurrence in previously dissected compartments. Bilateral MND (therapeutic for ipsilateral side and prophylactic for contralateral side) may be a therapy option for N1b PTC >4 cm and having extrathyroid extension.