Prophylactic neck dissection in papillary thyroid cancer: when is it necessary?

BACKGROUND The American Cancer Society estimates that there will be approximately 56,460 new diagnoses of thyroid cancer in the United States during 2012, and more than 90% will be papillary thyroid cancer (PTC). Despite the large, ever-increasing number of thyroid cancer cases, the ideal initial management of well-differentiated PTC remains controversial. The role of the prophylactic central neck dissection (pCND) has emerged as the most highly debated topic, with conflicting reports regarding indications, recurrence prevention, and reduction of cause-specific mortality. Currently, there is no argument that a formal, compartmental CND should be performed if preoperative or palpable nodal disease is encountered. However, the 2009 American Thyroid Association (ATA) guidelines state that, “Prophylactic central compartment neck dissection may be performed in patients with papillary thyroid carcinoma with clinically uninvolved central neck lymph nodes, especially for advanced primary tumors (T3 or T4; Grade C recommendation; expert opinion).” With the advent of personalized therapy based on molecular testing, the BRAF gene has shown the most promise in predicting lymph node metastases and may be used to direct clinicians on whether to perform a pCND. The focus of the review will seek to answer the question of best practice with regards to pCND in PTC. LITERATURE REVIEW Due to the excellent outcomes seen with PTC, the importance of lymph node metastases has been difficult to interpret. Recent, large, population-based studies have demonstrated a decrease in cause-specific survival in lymph-node positive PTC patients. Zaydfudim et al. used the Surveillance, Epidemiology, and End Results database to analyze outcomes of 30,054 patients with PTC. They concluded through multivariate analysis that metastatic LNs conveyed a 46% increased risk of death (HR, 1.46; P<.001) in patients 45 years, even with the majority of patients with excellent long-term survival. However, in patients< 45, lymph node status did not influence survival. While the presence of metastatic positive lymph nodes in PTC may dictate a decrease in cause-specific survival, does performing a prophylactic central neck dissection actually improve the patient’s outcome? A meta-analysis of five studies with a total of 1,264 patients demonstrated a decrease in lymph node recurrence (2% vs. 3.9%) in the thyroidectomy1pCND group, but this did not achieve statistical significance. The rate of transient recurrent laryngeal nerve paralysis (1.8%–5.4% thyroidectomy1pCND, 1%–1.3% thyroidectomy alone) and transient hypoparathyroidism (18%– 44% thyroidectomy1pCND, 8%–14% thyroidectomy alone (P< 0.02)) was higher in the group receiving pCND. Permanent recurrent nerve paralysis and hypocalcemia were not different between the two arms. The authors concluded that the balance between the risks and benefits favored thyroidectomy alone. However, they recognized several limitations to the study: inclusion of retrospective data, inconsistencies in the use of RAI and thyroid suppression postoperatively, limited data on timing of recurrence, and a lack of standardized reporting with regard to the extent of central neck dissection (ipsilateral vs. bilateral, etc.). The authors conclude with the call for a large, prospective trial to fully resolve the controversy. However, the feasibility of such a randomized trial was investigated by the ATA, which concluded that prohibitively large sample sizes (5,840 patients) and approximately $20 million would be required to demonstrate significant differences in outcomes. From the Louisiana State University Health Sciences Center– Shreveport, Department of Otolaryngology/Head and Neck Surgery, Shreveport, Louisiana, U.S.A.