Differentiated thyroid carcinoma:: The new UICC 6th edition TNM classification system in a retrospective analysis of 169 patients

Aim: To compare the new, 6th edition, UICC TNM staging system with the former edition, we updated TNM staging in patients with differentiated thyroid carcinoma. Methods: The new and old TNM classification systems for differentiated thyroid carcinoma were applied in a retrospective analysis of 169 patients who underwent therapy with radioiodine (I-131) from 1975 through 2002 at the Department of Nuclear Medicine, Frankfurt. Results: According to the new staging system, 83 patients (49%) were classified as T1 compared to 54 patients (32%) based on the former edition; 32 patients (19%) as T2 compared to 61 (36%) patients formerly. In 44 patients with minimal extrathyroid extension, formerly classified T4, the new TNM staging changed to T3, and no patient was classified T4. The one year relapse-free survival fraction under the former edition staging was 100% for T1 and 92.2% for T2, compared to 96.8% for new edition T1 and 93.3% for T2. Conclusion: The new TNM classification causes a significant change in staging. New T1 classified tumors had a slightly worse relapse-free survival fraction compared with the old T1 carcinomas. For patients treated at our department, the altered criteria for classifying extrathyroid extensions have had only a minor impact on disease management.