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Can We Restrict Selective Neck Dissection for Well-Differentiated Thyroid Cancer Based upon Preoperative Ultrasound?

Objectives: Describe the use of preoperative ultrasound lymphatic mapping to restrict the scope of neck dissection for thyroid cancer. Methods: Adults who underwent surgery for well-differentiated thyroid cancer with lateral neck metastases and had preoperative ultrasound lymphatic mapping were identified by billing codes. A retrospective review was performed. An ultrasound was determined to be diagnostically accurate if no false negative results were present. Results: 45 patients were included. Two patients underwent a comprehensive neck dissection levels I-V, 38 underwent a lateral neck dissection levels II-IV (level V included 23 times), and five underwent a more restricted selective neck dissection. Nine previously underwent lateral neck dissection, and 32 previously underwent thyroidectomy. Seven patients (15.5%) recurred in the contralateral neck or within the previously-dissected nodal basin. There were no recurrences in the ipsilateral neck outside the previously-dissected levels. Median follow-up was 771 days. Diagnostic accuracy for levels II-V was 76.1%, 81.6%, 89.8%, and 73.9% respectively. Grouped diagnostic accuracy for levels II-V was 46.7% (ie no errors in any level). Variables such as experience of ultrasonographer, delay between ultrasound and surgery, and previous surgery did not significantly influence the accuracy of ultrasound. Grouped positive predictive value of levels II-V was 80.4%. Conclusions: The current study suggests that it is feasible to restrict the scope of selective neck dissection for well-differentiated thyroid carcinoma based upon the findings of ultrasound lymphatic mapping. High positive predictive value indicates that if suspicious nodes are seen, they should be targeted. Undergoing comprehensive neck dissection did not protect against recurrence.