The Importance of Central Compartment Elective Lymph Node Excision in the Staging and Treatment of Papillary Thyroid Cancer

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Abstract
The incidence of lymph node (LN) metastasis in cases of well-differentiated thyroid carcinoma (WDTC) has been reported to be 20% to 90%.1-9 The reasons for this wide range are unclear, and controversy still remains regarding whether LN dissection needs to be performed at the time of thyroidectomy. Nodal metastasis to the central compartment is difficult to establish by clinical examination, yet the presence of nodal metastasis can influence the staging of WDTC in patients 45 years or older. Currently, staging of thyroid cancer is generally based on extent of the primary tumor, clinical examination, and radiographic findings, particularly the postthyroidectomy radioactive iodine survey scan. Therefore, according to the 2002 American Joint Committee on Cancer staging guidelines, T1 and T2 lesions in patients who are 45 years or older would be staged as stages I and II, respectively, if no abnormal adenopathy is detected by clinical examination, radiographic means, or intraoperatively. In this age group, a previously assigned stage I or stage II WDTC would be reassigned to stage III if nodal involvement is established in the level VI central compartment (paratracheal, pretracheal, or prelaryngeal). Knowledge of the central compartment nodal status is important for accurate staging and formulating an appropriate paradigm for subsequent cancer surveillance. It may also help determine whether the patient would benefit from adjuvant treatment with radioactive iodine and/or thyroxin suppression. Furthermore, in older patients, removal of positive LNs may have therapeutic benefits. Vini et al10 conducted a study that followed 111 patients who were 70 years or older with WDTC and found that 21% of them developed locoregional recurrent disease. In this older group of patients, recurrent disease occurred relatively soon after initial treatment. Studies suggest that there are biologic differences in the thyroid tumor cells of older patients that result in a reduced capacity to take up radioactive iodine. A study conducted by Schlumberger et al11 noted that only 53% of patients older than 40 years displayed radioactive iodine uptake at metastatic sites compared with 90% of patients younger than 40 years. Therefore, treatment with radioactive iodine may not be effective in treatment of residual nodal metastasis in the older patient population. In those patients' tumors that are not iodophilic, excision of central compartment LNs may be therapeutic and may reduce recurrence in this compartment. Thus, elective excision of central compartment LNs at the time of thyroidectomy for papillary cancer would provide staging information that is more accurate and may have therapeutic and prognostic implications, particularly for patients who are 45 years or older. Previous studies1-7 have reported the incidence of cervical LN metastasis from papillary carcinoma but not specifically the incidence in the older age group. It is for this older group that there may be therapeutic and prognostic implications if their tumors are restaged from N0 to N1a. This study aims to determine the true incidence of LN metastasis to central compartment in the older vs younger age groups by routinely exploring and/or dissecting that compartment in patients diagnosed with papillary carcinoma.