Prognostic value of the sixth edition AJCC/UICC TNM classification for differentiated thyroid carcinoma with extrathyroid extension

Context: The prognostic value of the sixth edition AJCC/ UICC TNM classification is currently unclear. Objective: The aim was to evaluate the prognostic value of the sixth edition. Design and Patients: We retrospectively assessed 354 primary differentiated thyroid carcinomas ( 77 men and 277 women; age, 51.2 yr; follow- up, 107.6 months) between 1964 and 2003. Sixty percent of patients underwent lobectomy, 40% underwent subtotal/ total thyroidectomy, and only 2% were given radioiodine. There were 153, 104, 86, and 11 patients in fifth stages I, II, III, and IV, and 175, 76, 14, 68, 10, and 11 patients in sixth stages I, II, III, IVA, IVB, and IVC, respectively. Results: New T1 - 3 had no significant influence. In Cox proportional hazard analysis, T4a and T4b were significantly related to disease-specific survival ( DSS). We separately analyzed 68 patients ( age 45 yr or older) with extrathyroid extension. These T4 ( fifth) tumors were reclassified as 6 T3, 52 T4a, and 10 T4b tumors. The 10-yr DSS rates were 100, 69.3, and 10.0% for T3, T4a, and T4b, respectively. T4b exhibited worse prognoses compared with T4a ( P < 0.0001; hazard ratio, 10.1; 95% confidence interval, 4.1 - 25.3). Stages I and II in both editions achieved favorable prognoses. The 10- yr DSS rates were 67.0 and 27.3% in fifth stages III and IV, and 100, 74.5, 10.0, and 27.3% in sixth stages III, IVA, IVB, and IVC, respectively. DSS curves differed significantly between all sixth TNM stages ( P < 0.0001). Conclusion: The sixth edition more accurately predicts different outcomes according to the revised criteria for the degree of extrathyroid extension.