Some recent guidelines recommend unilateral thyroidectomy for low-risk differentiated thyroid cancer (DTC) sized > 1 and < 4 cm. The present study was designed to evaluate the proper extent of thyroidectomy for patients who have DTC sized > 1 and < 4 cm.

From April 1967 to December 2011, a total of 16,065 DTC patients underwent thyroidectomy at Yonsei University Hospital. Among them, 5,427 (33.7%) patients were classified as having DTC > 1 and < 4 cm and were enrolled in this study. Clinicopathologic features and prognostic results (disease-free and disease-specific survival rates) were analyzed by retrospective medical chart review. The mean follow-up duration was 57.3 ± 58.1 months.

In the subtypes of tumors, papillary thyroid carcinoma (PTC) was the most common cancer (96.9%) and follicular and poorly differentiated carcinoma comprised 2.7 and 0.1% respectively. The mean tumor size was 1.84 ± 0.74 cm. Patients had extrathyroidal extension (69.3%), multiplicity (35.0%), bilaterality (26.3%), central lymph node metastasis (35.8%), and lateral neck node metastases (20.2%). Of a total of 5,427 patients, 4,353 (80.2%) underwent total thyroidectomy and 1,043 (19.2%) patients underwent less- than-total thyroidectomy. The recurrence rates in total thyroidectomic and less-than-total thyroidectomic groups were 3.9 and 10.0% respectively. The less-than-total thyroidectomic group showed lower disease-free survival (DFS) rate (p= 0.039) and higher disease-specific survival (DSS) (p = 0.035) rate compared with the total thyroidectomic group. In multivariate analysis for DFS, tumor size, N stage, and the extent of thyroidectomy were independent risk factors. In multivariate analysis for DSS, age, gender, tumor size, and N and M stage were independent risk factors.

In patients with tumor size > 1 and ≤ 4 cm, total thyroidectomy was beneficial in reducing recurrence. However, our study confirmed that risk factors for DSS were not the extent of thyroidectomy but traditional prognostic factors, such as older age, male sex, large tumor size, lymph node metastasis, and distant metastasis.