The Multicentre Study Differentiated Thyroid Cancer (MSDS) collective represents a well defined group of patients with locally aggressive thyroid carcinomas (pT4; AJCC/UICC 1997). The aim of the present study was to compare the survival of patients with minimum and extensive extrathyroidal growth according to the new AJCC/UICC TNM staging system 2009.
Patients, methods: The follow-up data of 347 patients were analysed. Patients were reclassified according to the current AJCC/UICC 2009 classification. The event-free and overall survival was evaluated using Kaplan-Meier analysis. In addition, postoperative complications and status of disease were documented.
Results: 327 patients were assigned to stage pT3 and 20 patients to stage pT4a, respectively. Median follow-up was 6.1 years (range 0.04-9.8 years). 92.5% of patients reached complete remission. There were 7.8 % recurrences in the thyroid bed, in locoregional lymph nodes and/or in distant sites. The overall survival was >98% both in pT3 and pT4a patients (p = n. s.). In contrast, the event-free survival was significantly less favourable in pT4a patients (p < 0.001). Using multivariate analysis the following parameters were significant predictors of event-free survival: histological tumour type, degree of extrathyroidal extension and nodal metastasis (p < 0.05).
Conclusions: The MSDS patients with locally aggressive differentiated thyroid cancer showed an excellent overall survival during a median follow-up of 6.1 years. According to the current AJCC/UICC 2009 classification, pT3 patients with minimal extrathyroidal extension revealed a significantly better event-free survival than pT4a patients with extensive extrathyroidal growth.
Trial registration: ClinicalTrials.gov NCT00144079.