분화성 갑상선암의 갑상선 절제술과 림프절 절제술 범위의 결정 = Decision of the Extent of Thyroid Resection and Lymphadenec-tomy

다국어 초록 (Multilingual Abstract)

Most patients with papillary thyroid cancer (PTC) are low risk and have an excellent prognosis. But in low-risk patients with PTC the extension of thyroidectomy and neck node dissection remains controversial. To date, no randomized, prospective trial comparing survival duration and recurrence rates after thyroid lobectomy and total thyroidectomy has been performed. Proponents of thyroid lobectomy assert that for most patients younger than the age of 40 to 50 years with tumors confined to the thyroid gland the higher complication rates after total thyroidectomy outweigh their potential benefits with respect to disease-free and overall survival. Those who favor total thyroidectomy emphasize advantages such as clearing microscopic contralateral disease, enabling the use of radioactive iodine as an adjuvant therapy, allowing accurate postoperative thyroglobulin surveillance and possibly providing better survival. Therefore the treatment decisions should be based on risk group analysis. The understanding of the prognostic factors and risk groups is crucial in the management of well differentiated thyroid cancer. The important prognostic factors are age, grade of tumor, extrathyroidal extension, size of tumor, and distant metastases. Most consensus guidelines recommend total thyroidectomy as the preferred initial procedure for patients with PTC, with absolute indications including a past history of radiation exposure, familial thyroid cancer, known extrathyroidal extension, cervical lymph node or distant metastasis, tumor size ＞4 cm, and an aggressive histologic variant of papillary thyroid cancer. In addition to thyroidectomy, lateral neck dissection should be done for palpable or biopsy-positive lymph nodes identified on the preoperative ultrasound. Even though up to 80% of patients will have at least microscopic metastatic spread to cervical lymph nodes, this does not seem to affect prognosis, at least in patients younger than 45 years, and prophylactic lateral neck dissection for patients with papillary thyroid cancer is not recommended. Evidence based recommendations support the application of central lymph node dissection (CLND) at the initial operation for differentiated thyroid cancer in expert hands. CLND may decrease recurrence of PTC and likely improves disease-specific survival because reoperation in the central neck compartment for recurrent PTC may increase the risk of hypoparathyroidism and unintentional nerve injury.