OP66 – Reassessment of Differentiated Thyroid Cancer Patients Using the 8th TNM classification System: a comparative study

      Benbassat, Carlos1,3Muallem Kalmovich, Limor2,3; Steinschneider, Miriam1,3; Koren, Shlomit1,3; Or, Karen1 ; Cantrell, Dror1 1 Endocrine Institute, Assaf Harofeh Medical Center, Zerifin, Israel 2 Head and Neck Surgery Unit, Department of ENT, Assaf Harofeh Medical Center, Zerifin, Israel 3 Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel   Background: Based on the prevailing concept that over-diagnosis with no change in mortality drives the increased incidence of differentiated thyroid cancer (DTC), considerable modifications have been introduced in the new TNM staging edition. Aims: We aimed to compare a same group of DTC patients before and after re-staging for mortality, disease severity and disease outcome. Methods: From our thyroid cancer registry, 431 DTC patients were re-staged according to the 8th edition and compared to the 7th for clinico-pathological data, treatment modalities and outcome. Mean follow-up was 9 years. Results: Using the 8th edition, 97.5% patients filled in stage I-II category versus 76.4% before, of whom 28.2% were at intermediate/high risk compared to 16.7% before (p=0.001). Disease specific mortality (DSM) in stage I-II was 0% (0/11) for edition 7 and 1.5% (6/11) for edition 8 (p=0.069). Persistency rates at 1 year and last visit were 25.5% vs 16.6% (p=0.013) and 15% vs 10% (p=0.08) for stage I-II and 56.5% vs 33.3% (p=0.07) and 42.8% vs 18.7% (p=0.045) for stage II only. Of 124 patients in the 45-54 age-range, 37 shifted from stage III-IV to stage I-II, 62% were intermediate/high risk, 42% had persistency at 1 year and 22% at last visit, and DSM was 5.4%. In this group, distant metastases at diagnosis and all-time were 14.3% and 22.2%, respectively. Conclusion: The new TNM classification appears to underestimate disease severity, outcome and mortality in a considerable group of patients. Larger studies are needed to validate our results   References:
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