The Role of Prophylactic Central Neck Dissection in the Treatment of Differentiated Thyroid Cancer

摘要

The utility and efficacy of prophylactic central neck dissection with total thyroidectomy for the treatment of differentiated thyroid cancer has been debated in the literature over the past few decades. Proponents of prophylactic central neck dissection support its routine use with the notion that it reduces local recurrence, increases accuracy in TNM staging, and reduces surgical morbidity associated with reoperation. Conversely, those against the use of routine prophylactic central neck dissection argue there is no clear evidence which shows a reduction in recurrence or added benefit to survival, while the procedure increases the risk for complications and morbidity. This article discusses the role of prophylactic central neck dissection in the setting of thyroid cancer and reviews recently published literature to evaluate efficacy and safety of this procedure.Keywords: Differentiated thyroid cancer, morbidity, prophylactic central neck dissection, recurrence, survival, treatmentINTRODUCTIONThyroid cancer is the most common endocrine malignancy, and its incidence is increasing at the highest rate among cancers in both the US and worldwide.1,2 The National Cancer Institute’s annual Surveillance Epidemiology and End Results (SEER) database estimates that there will be 62,450 new cases of thyroid cancer in the US in 2015, with an incidence of 13.5 per 100,000.1 The absolute increase in the incidence of thyroid cancer is estimated to be 9.4 per 100,000 individuals, with papillary thyroid cancer (PTC) accounting for the majority of these cases. Overall, differentiated thyroid cancer (DTC) has a 10-year survival rate of greater than 90%. However, despite its promising survival rate, local recurrence occurs in 20%–30% of papillary thyroid cancer patients due to clinically undetectable metastasis to cervical lymph nodes.3 Cervical lymph node metastases are a common feature of PTC, occurring primarily in the central compartment (level VI) with an incidence between 20% and 90% (average 60%).4–8 Conversely, follicular thyroid cancer (FTC) often spreads hematogenously, and rarely metastasizes to the cervical lymph nodes.9 Hurthle cell thyroid cancer (HTC) is a rare and aggressive form of differentiated thyroid cancer of follicular cell origin; HTC displays a lower rate of cervical lymph node metastasis compared to PTC.9The central compartment is bounded by the hyoid bone (superior), carotid artery (lateral), and sternal notch or innominate artery (inferior). The American Thyroid Association (ATA) defines central compartment neck dissection as “comprehensive, compartment-oriented removal of the prelaryngeal and pretracheal nodes and at least one paratracheal lymph node basin.”10 The regional metastases to the cervical lymph nodes were traditionally believed to have an effect only on recurrence rate, but not mortality.5,8,11 However, in 2006, a population-based study from Sweden found lymph node metastases in both the central and lateral compartments to be a prognostic factor for patients with DTC.11 This finding complicated debate in the literature with regard to the initial treatment of differentiated thyroid cancer.5,8,11 Surgery, typically in the form of a total thyroidectomy (TT), has been accepted as the treatment of choice for most patients with differentiated thyroid cancer. There is also consensus in regard to treating patients with clinically evident level VI nodal disease with central neck dissection at the time of initial surgery.4–8 However, the addition of a prophylactic central neck dissection (PCND) to TT in clinically node-negative patients with DTC remains controversial due to lack of prospective randomized controlled studies.4,12 The ATA addresses this controversy in the 2015 American Thyroid Association Guidelines for Adult Patients with Thyroid Nodules and DTC, recommending the following for the use of PCND in the treatment of DTC:(b) Prophylactic central-compartment neck dissection (ipsilateral or bilateral) sh