Risk Factors for Recurrence After Treatment of N1b Papillary Thyroid Carcinoma

Objectives: To examine risk factors for posttreatment recurrence in papillary thyroid carcinoma (PTC) patients with initial presentation of lateral neck metastasis (N1b). Summary of Background Data: N1b PTC recurs after definitive treatment. Methods: Study subjects were 437 consecutive PTC patients who underwent total thyroidectomy and therapeutic neck dissection of central and lateral compartments and postoperative radioactive iodine ablation therapy. The patients' demographics and pathological factors, including factors related to tumors and lymph nodes (LNs), and postoperative thyroglobulin levels were reviewed. Univariate and multivariate Cox proportional hazards regression analyses were used to identify factors associated with recurrence-free survival (RFS). Results: During a median follow-up of 83 months (range, 32-135 months), recurrence occurred in 81 (18.1%) patients. Univariate analyses showed that male sex, tumor size, macroscopic extrathyroidal extension, perineural invasion, extranodal extension, LN involvement, LN ratio, MACIS score, and postoperative serum levels of thyroglobulin were significantly associated with RFS (P < 0.05). Multivariate analyses revealed that LN ratio (> 0.25) in the lateral compartment (adjusted hazard ratio = 2.099, 95% confidence interval = 1.278-3.448; P = 0.003), and postoperative serum levels of stimulated (>5.0 ng/mL; 3.172, 1.661-6.056, P < 0.001) and unstimulated (>0.1 ng/mL; 3.200, 1.569-6.526, P = 0.001) thyroglobulin were independent predictors of any-site RFS. Clinical and tumor factors were not independent predictors of RFS outcomes (P > 0.1). Conclusions: Posttreatment recurrence is predicted by the LN ratio in the lateral compartment and postoperative serum levels of thyroglobulin in patients with metastatic PTC in the lateral neck.