Comparison of initial risk stratification methods in predicting treatment outcome in differentiated thyroid cancer

Abstract

Introduction: Differentiated thyroid cancer (DTC) is the commonest endocrine malignancy. With accurate risk stratification, low-risk patients can be treated with less intensive treatment and follow-up. We reviewed outcomes of DTC in our hospital and evaluated different staging methods in predicting survival. Methods: This was a retrospective review including 321 patients with DTC treated in our hospital from 1994 to 2005. The cases were assessed for risk of recurrence using different risk stratification methods available at the time. Disease-free survival (DFS) and overall survival (OS) of each method were analysed by comparing their Kaplan- Meier plots with log rank tests. The Harrell C-index was used to evaluate the discriminative ability of different risk stratification methods in identifying low- or high-risk cases. Results: The 10-year DFS and OS were 90.9% and 93%, respectively. Comparing the C-indices, the European Organisation for Research and Treatment of Cancer (EORTC) had the highest discriminative power for predicting recurrence (C-index = 0.694, 95% confidence interval [CI] = 0.599-0.79) and OS (C-index = 0.825, 95% CI = 0.725-0.924). The MD Anderson Cancer Center (MDA) came in second for predicting recurrence (C-index = 0.669, 95% CI = 0.584-0.753) and OS (C-index = 0.769, 95% CI = 0.690-0.849). The commonly used American Joint Committee on Cancer and the International Union Against Cancer/Tumour, Node, Metastasis system (AJCC/UICC TNM) staging ranked third for predicting recurrence (C-index = 0.651, 95% CI = 0.561-0.740) and OS (C-index = 0.747, 95% CI = 0.630-0.863). Conclusions: All risk stratification methods were reliable tools for initial risk stratification in DTC. We recommend the use of AJCC/UICC TNM or MDA methods for their practicality.