When Is Prophylactic Neck Dissection in Papillary Thyroid Cancer 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 pre-operative or palpable nodal disease is encountered. However, the 2009 American Thyroid Association (ATA) guidelines state that pCND may be performed in patients with PTC with clinically uninvolved central neck lymph nodes, especially for advanced primary tumors. 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.

Best Practice

Based on large, population studies, one can infer that the presence of metastatic lymph nodes in patients with PTC does predict poorer survival for patients  > 45. The results of the meta-analysis mentioned above suggest that the use of pCND for all PTC patients is not warranted since the risks of transient nerve paralysis and hypoparathyroidism may outweigh the benefits. While the true advantage of prophylactic CND for PTC with regard to recurrence prevention and improved survival may be impossible to ascertain, the presence of metastatic lymph nodes should be investigated for staging and post-operative treatment planning in high-risk patients.

The questions then arise: 1) Which patients are high-risk for central neck metastases? 2) In which patients will the presence of nodal disease dictate treatment? In general all patients with pathologically confirmed PTC should undergo a pre-operative investigation for metastatic lymphadenopathy. However, the thyroid can obstruct the ultrasonographic view of the central compartment. Therefore, the 2009 ATA guidelines suggest that pCND may be performed in patients with clinically-staged T3/4 PTC disease, tumor size > 4cm, or presence of extrathyroidal extension, which has been confirmed as risk factors for occult lymph node metastases in other studies. The presence of a BRAF mutation, detected preoperatively on FNA, confers a 2.8-fold increase in the risk for occult central compartment metastases. Hence, the use of molecular testing for BRAF may further improve the ability to identify patients in need of a prophylactic central neck dissection. Finally, due to the overall excellent prognosis seen with PTC, prophylactic CND is a procedure with potential for increased iatrogenic harm and questionable benefit, implying that a surgeon’s comfort level with the procedure should also be taken into consideration. Read the full article in The Laryngoscope.