A Vision for the Surgical Management of Papillary Thyroid Carcinoma: Extensive Lymph Node Compartmental Dissections and Selective Use of Radioiodine

Abstract

The natural history of papillary thyroid cancer (PTC) is such that many patients reach normal life expectancy after total thyroidectomy and radioiodine therapy (1). Still, a large number of patients experience locoregional recurrences, usually in cervical lymph nodes, and within 10 yr of initial therapy, about 7% die of disease (2). Yet despite the slow tumor growth and favorable prognosis for survival of patients with small PTCs, the major challenge is controlling locoregional recurrence. Whether this is best accomplished with surgery or radioiodine—or whether they should be treated at all—has been a matter of debate, especially in patients with microcarcinomas. What are the risks of lymph node metastases? The initial management of small PTCs has received considerable attention stemming from the relentlessly increasing incidence of small PTCs that has been observed over the past three decades in the United States (3). Nearly half were papillary microcarcinomas 1 cm or smaller, and nearly 90% were PTCs 2 cm or smaller, both of which have favorable survival rates. Yet a study of over 52,000 patients found the recurrence rate to be 4.6% for tumors smaller than 1 cm and 7.1% in patients with tumors 1–1.9 cm, with 10-yr cancer-specific mortality rates of 2 and 2.6%, respectively (4). To obfuscate initial management decisions further, the rates of lymph node metastases in both lowand high-risk patients range from 25 to 60%, depending upon the extent of surgery (5, 6). Although regional lymph node metastases have generally been regarded to increase local recurrence rates without affecting survival, several large studies suggest otherwise. A study of almost 10,000 patients found the 14-yr survival rate was 82% for patients with and 79% for patients without lymph node metastases (P 0.05) (7). Another study (8) of 33,088 patients found a 46% increased risk for death with lymph node metastases in patients with follicular thyroid cancer and in patients 45 yr or older with PTC (P 0.001) (8). Lastly, residual metastatic lymph nodes that remain after initial therapy are the most common cause of subsequent recurrence (5, 6). These facts sharply focus the debate concerning initial therapy for lymph node metastases, especially concerning the risks and benefits of surgery and radioiodine remnant ablation. What are the risks and benefits of central lymph node dissection? For lymph node metastases, the American Thyroid Association (ATA) guidelines (9) suggest systematic neck lymph node dissection, which refers to en bloc dissection of anatomic neck compartments, as compared with selectively excising lymph nodes (“berry picking”), which is not recommended. Prophylactic dissection denotes removal of lymph nodes that are considered normal preoperatively or intraoperatively, and therapeutic dissection refers to removal of malignant lymph nodes identified before or during surgery. The ATA guidelines under revision suggest that prophylactic central-compartment neck dissection (ipsilateral or bilateral) may be performed in patients with PTC with clinically uninvolved central neck lymph nodes, especially for advanced primary tumors (T3 or T4), which is a Grade C Recommendation (Expert Opinion), and that near-total or total thyroidectomy without prophylactic central neck dissection may be appropriate for small (T1 or T2) noninvasive clinically node-negative PTCs and most follicular cancers (Grade C Recommendation). The ATA guidelines suggest preoperative cervical ultrasonography in all patients undergoing thyroidectomy. Although this may identify suspicious cervical adenopathy in up to half the cases, potentially altering the surgical approach in many patients, it has several limitations, particularly in evaluating extracapsular invasion in deep locations in the neck and lymph node metastasis in the central neck, which may lower the sensitivity of ultrasonography to 35% (10).