Evaluation of the seventh edition of the American Joint Committee on Cancer tumournodemetastasis (TNM) staging system for patients undergoing curative resection of hepatocellular carcinoma: implications for the development of a refined staging system

Objectives This study aimed to evaluate the seventh edition of the American Joint Committee on Cancer (AJCC) tumournodemetastasis (TNM) staging system and to compare its efficacy with those of the fifth and sixth editions of the AJCC staging system and the TNM staging system defined by the Liver Cancer Study Group of Japan. Methods Data for 754 patients submitted to hepatectomy for hepatocellular carcinoma (HCC) between 1989 and 2005 were reviewed. Tumour-free survival was estimated using the KaplanMeier method and compared between subgroups using the log-rank test. Prognostic factors for tumour-free survival were identified by multivariable analysis. The accuracy of these staging systems was evaluated using the Cox regression model and a refined staging system was developed based on the drawbacks of the respective systems. Results According to the criteria defined by the seventh AJCC TNM staging system, 5-year survival was 50.6% in patients with T1 tumours, 21.0% in patients with T2 tumours, 14.6% in patients with T3a tumours, 12.1% in patients with T3b tumours, and 12.9% in patients with T4 tumours. There was no survival difference between patients with T3a and T3b tumours (P = 0.073), nor between those with T3b and T4 tumours (P = 0.227). Significant prognostic tumour factors were microvascular invasion, tumour multiplicity, bilobar disease and a tumour size of 5.0cm. The fifth and sixth editions of the AJCC TNM staging system were found to be more accurate in prognosis than the seventh. Conclusions The seventh edition of the AJCC TNM staging system is able to adequately stratify patients with early HCC only. A refined staging system is therefore proposed.