Primary tumour size is a prognostic parameter in patients suffering from differentiated thyroid carcinoma with extrathyroidal growth: results of the MSDS trial

Objective: The Multicentre Study Differentiated Thyroid Cancer (MSDS) collective represents a well-defined group of patients with thyroid carcinomas with extrathyroidal extension. The aim of the present study was to evaluate the relationship of the primary tumour size with clinicopathological features as well as the outcome of patients with minimum and extensive extrathyroidal growth (pT3b- and pT4a-tumours; UICC 2002/2003, 6th ed). Methods: The tumour diameter was available in 324 out of 351 MSDS patients (244 females, 80 males). Mean age of patients was 47.7 +/- 12.0 years (range, 20.1-69.8 years), and the median follow-up was 6.2 years. The relationship between primary tumour size and the following clinicopathological data was investigated: age, gender, histological tumour type (papillary thyroid carcinomas (PTC) versus follicular thyroid carcinomas (FTC)) and UICC/AJCC TNM classification. In addition, the correlation between primary tumour size and event-free and overall survival was assessed. Results: The FTC of our series were significantly larger than PTC (3.46 vs 1.84 cm; P<0.001). Patients suffering from pT3b-tumours presented with significantly smaller tumour size than those with extensive extrathyroidal growth (pT4a-tumours) (1.9 vs 3.0 cm; P<0.01). All patients with distant metastases suffered from tumours >2 cm. Furthermore, event-free and overall survival were significantly correlated with increasing tumour size (P<0.05). Using multivariate analysis, a pT4a-category and a tumour diameter >2 cm remained independent predictors of survival. Conclusions: In patients suffering from differentiated thyroid carcinoma with extrathyroidal growth (pT3b and pT4a), the tumour size is an independent predictor of event-free and overall survival.