Critical appraisal of TNM versus HKU staging system for postoperative prognostic evaluation of hepatocellular carcinoma

BACKGROUND: The 8(th) edition of the American Joint Committee on Cancer tumor-node-metastasis staging system (AJCC 8(th)) has been launched with modifications in T staging. The University of Hong Kong liver cancer staging system (HKUSS) has been proven to better categorize hepatocellular carcinoma (HCC) into different T stages. This study aimed to compare the two systems’ predictive ability for HCC recurrence after primary surgical resection. METHODS: Patients who had primary, curative resection for HCC between 1989 and 2017 were reviewed. The Kaplan-Meier plot was used to estimate disease-free survival (DFS), and the log-rank test was used for survival comparison between subgroups. The two systems’ prediction of recurrence was evaluated by the Cox regression model. RESULTS: Totally 1,815 patients were included. With AJCC 8(th), the 5-year DFS was 58.9% for T1a, 52.3% for T1b, 30% for T2, 16.9% for T3, and 14.4% for T4. No survival difference was demonstrated between T1a and T1b (P=0.668) or between T3 and T4 (P=0.562). With HKUSS, the 5-year DFS was 57.7% for T1, 43.4% for T2, 28.9% for T3, and 15.7% for T4. The T staging in HKUSS showed significant survival differences (T1 vs. T2, T2 vs. T3, and T3 vs. T4; P<0.001). Using receiver operating characteristic curves to show the recurrence status in the two systems, HKUSS had the largest area under curve (AUC) (HKUSS: AUC =0.655, SE 0.014, P<0.001, 95% CI, 0.628–0.681; AJCC 8(th): AUC =0.652, SE 0.013, P<0.001, 95% CI, 0.625–0.677). CONCLUSIONS: HKUSS showed better categorization of HCC. In the context of primary surgical resection, HKUSS may be more appropriate for stratification of patients with HCC with various T stages, and thus the choice of staging system when primary surgical resection is considered for patients of HCC.