Occult lymph node metastasis and risk of regional recurrence in papillary thyroid cancer after bilateral prophylactic central neck dissection: A multi-institutional study

Background. The impact of occult lymph node metastasis on regional recurrence after prophylactic central neck dissection for preoperative, nodal-negative papillary thyroid cancer is controversial. We investigated risk factors for regional lymph node recurrence in papillary thyroid cancer patients who underwent total thyroidectomy and bilateral prophylactic central neck dissection. Analysis was according to clinicopathologic characteristics and occult lymph node metastasis patterns. Methods. This multicenter study enrolled 211 consecutive patients who underwent total thyroidectomy with bilateral prophylactic central neck dissection for papillary thyroid cancer without evidence of central lymph node metastasis on preoperative imaging. Clinicopathologic features and central lymph node metastasis patterns were analyzed for predicting regional recurrence. Multivariate Cox regression analysis was used to identify independent factors for recurrence. Results. Median follow-up time was 43 months (24-95 months). Ten patients (4.7%) showed regional lymph node recurrence. The estimated 5-year, regional recurrence-free survival was 95.2 %. Tumor size 1 cm, central lymph node metastasis, lymph node ratio, and prelaryngeal lymph node metastasis were associated with regional recurrence in univariate analysis (P < .05). In multivariate analysis, a lymph node ratio 0.26 was a significant risk factor for regional lymph node recurrence (odds ratio = 11.63, P = .003). Lymph node ratio >= 0.26 was an independent predictor of worse recurrence-free survival on Cox regression analysis (hazard ratio = 11.49, P = .002). Conclusion. Although no significant association was observed between the presence of occult lymph node metastasis and regional recurrence, lymph node ratio >= 0.26 was an independent predictor of regional lymph node recurrence in papillary thyroid cancer patients who underwent total thyroidectomy and bilateral prophylactic central neck dissection.