A proposal for T1 subclassification in hepatocellular carcinoma: reappraisal of the AJCC 8th edition

Background: In the 8th edition of American Joint Committee on Cancer (AJCC) staging system for hepatocellular carcinoma (HCC), tumor size is not considered in T1 stage. The present study aimed to find out the optimal cutoff for tumor size to further stratify patients with T1 HCC. Methods: Operated HCC patients were identified from the Chang Gung Research Database (CGRD), and the patients with T1bN0M0 tumors were further divided into two groups based on the tumor size. The resulting subgroups were denoted as T1b (≤ cutoff) and T1c (> cutoff). The survivals were compared between T1a/b and T1c as well as T1c and T2. Results: From 2002 to 2018, a total of 2893 patients who underwent surgery for T1N0M0 HCC were identified from the CGRD. After excluding cases who died within 30 days of surgery, Kaplan–Meier survival analysis discovered that T1 tumors > 65 mm (T1c) had survivals similar to those of T2N0M0 tumors. Cox regression multivariate analysis further demonstrated that tumor size > 6.5 cm was an independent poor prognostic indicator for T1 HCC. Sensitivity tests also confirmed that tumors lager than 6.5 cm were significantly more likely to develop both tumor recurrence and liver-specific death after surgery. Conclusions: Our study demonstrated that tumor size would significantly impact the survival outcome of T1 HCC after surgery. Due to significantly worse survival, we proposed a subclassification within T1 HCC, T1c: solitary tumor > 6.5 cm without vascular invasion, to further stratify those patients at risk. Further studies are mandatory to validate our findings.