Staging systems for follicular thyroid carcinoma: application to 171 consecutive patients treated in a tertiary...

A number of risk-group stratification or staging systems have been found useful at stratifying patients with differentiated thyroid carcinoma into risk groups. Those identified as high risk could be subjected to more aggressive treatment, while those at low risk could be spared of such treatment. However, the best stratification system in patients with follicular thyroid carcinoma (FTC) remains unclear. Through a comprehensive MEDLINE search from 1965 to 2005, a total of 18 different staging systems were identified in the literature and 14 of them were applicable to 171 patients, with FTC managed at our institution from 1961 to 2001. Cancer-specific survivals (CSS) were calculated by Kaplan-Meier method and were compared by log-rank test. Using Cox proportional hazards analysis, the relative importance of each staging system in determining CSS was calculated by the proportion of variation in survival time explained (PVE). CSS were predicted by 13 out of the 14 staging systems significantly (P < 0.001). The three highest ranked staging systems by PVE were the new American Joint Committee on Cancer/Union Internationale Centre le Cancer 6th edition, tumour, node, metastases (TNM; 22.4), followed by the Clinical Class (21.2) and the metastases, age, completeness of resection, invasion, size (MACIS; 20.4). In conclusion, 13 out of the 14 presently available staging systems predicted CSS significantly in FTC. When predictability was measured by PVE, the TNM system was found to have the best predictability and thus, should be the stratification system of choice for FTC in the future.