Restaging of differentiated thyroid carcinoma by the sixth edition AJCC/UICC TNM staging system: stage migration and predictability.
BACKGROUND
The AJCC/UICC TNM staging system (TNM) is a widely accepted system for differentiated thyroid carcinoma (DTC). The objective of the present study was to evaluate the potential changes in cancer-specific survival (CSS) after reclassification from fifth to sixth edition TNM.


METHODS
A total of 760 DTC patients managed at our institution from 1961 to 2001 were retrospectively restaged from the fifth to sixth edition TNM. CSS were calculated using Kaplan-Meier method and were compared by the log-rank test. The relative ability of each edition in predicting CSS was calculated by the proportion of variance explained (PVE).


RESULTS
Upon reclassification, the proportion of T1 and T3 tumors increased from 14.2 to 33.4% and 10.0 to 33.7%; T2 and T4 decreased from 44.2 to 25.0% and 31.6 to 7.9%, respectively; N0 remained unchanged at 66.0%; N1a decreased from 25.7 to 4.7%; N1b increased from 8.4 to 29.3%; stages I and IV tumors increased from 55.7 to 60.3% and 3.4 to 17.6%, respectively; stages II and III tumors decreased from 20.5 to 13.9% and 20.4 to 8.2%, respectively. The sixth edition had a higher PVE value than the fifth edition. Significant differences in CSS were observed between stage III (fifth edition) and stage III (sixth edition) and between stage IV (fifth edition) and stage IVA (sixth edition).


CONCLUSIONS
The sixth edition TNM caused marked changes in the pT, pN and allocation of patients into different tumor stages. It appeared to have superior predictability over the fifth edition.
Lang
Brian
B
Division of Endocrine Surgery, Department of Surgery, University of Hong Kong Medical Centre, Queen Mary Hospital, 102 Pokfulam Road, Hong Kong SAR, China.
Lo
Chung-Yau
CY
Chan
Wai-Fan
WF
Lam
King-Yin
KY
Wan
Koon-Yat
KY
D000230:Adenocarcinoma / Q000473:pathology / Q000556:secondary / Q000628:therapy; D018263:Adenocarcinoma, Follicular / Q000473:pathology / Q000556:secondary / Q000628:therapy; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002291:Carcinoma, Papillary / Q000473:pathology / Q000556:secondary / Q000628:therapy; D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000556:secondary / Q000628:therapy; D002454:Cell Differentiation; D002648:Child; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008207:Lymphatic Metastasis / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology; D009367:Neoplasm Staging; D011379:Prognosis; D015996:Survival Rate; D013964:Thyroid Neoplasms / Q000473:pathology* / Q000628:therapy