Low-risk differentiated thyroid cancer: the need for selective treatment

The well recognized prognostic factors in differentiated carcinoma of the thyroid are age, grade, extracapsular extension, distant metastasis, and size of the tumor. Based on these prognostic factors, we have divided patients into low-, intermediate-, and high-risk categories. Clearly, there are significant differences in these three groups. This article analyzes in depth our data on low-risk thyroid cancer patients.

A retrospective review of 1,038 patients with differentiated carcinoma of the thyroid was undertaken. Various prognostic factors and risk groups were analyzed. Univariate and multivariate analyses were performed, and the survival curves were plotted by the Kaplan-Meier method. The inclusion criteria for the low-risk group were age younger than 45 years, tumors < 4 cm in size, low-grade histology, absence of distant metastasis, and absence of extrathyroidal extension. There were 465 patients in the low-risk group. Four hundred three patients had papillary and 62 patients had follicular thyroid cancer. There were 120 male and 354 female patients. Two hundred seventy-eight patients (60%) presented with clinically apparent lymph node metastasis.

With a median follow-up of 20 years, the 10- and 20-year survival in this select group was 99%. The local, regional, and distant recurrence rates were 5, 9, and 2% in this series. The analysis of the data showed statistical difference in local recurrence rate between partial lobectomy and total lobectomy (27 vs. 4%; p = 0.005). There was no statistical difference in local recurrence rate between total lobectomy compared with total thyroidectomy (4 vs. 1%; p = 0.10). The overall failure rate between partial lobectomy and total thyroidectomy (27 vs. 8%) was statistically significant (p = 0.04). There was no statistical difference in the overall failure rate between total lobectomy and total thyroidectomy (13 vs. 8%; p = 0.06). There was no survival difference between various histologies or nodal status.

Patients with low-risk tumors have excellent long-term survival. Nodulectomy or partial lobectomy should be avoided. The intraoperative decisions regarding the extent of thyroidectomy should be based on gross clinical findings and risk group analysis.