Redefining the T1 category of the 8th American Joint Committee on Cancer Staging System for intrahepatic cholangiocarcinoma: A SEER database analysis

The T1 tumor category is further divided into T1a (≤5 cm) and T1b (>5 cm) by tumor size in the 8th edition of the American Joint Committee on Cancer (AJCC) staging system for intrahepatic cholangiocarcinoma (ICC). The aim of the present study was to investigate the association between tumor size and prognosis in patients with T1 ICC. The data regarding patients with ICC was downloaded from the Surveillance, Epidemiology, and End Results database between January 2004 and December 2013, at the time of first diagnosis and entered into the database. Demographic and pathological characteristics of patients were analyzed using an independent t-test and χ² test. Overall survival was evaluated using Kaplan-Meier analysis; the cut-off point for tumor size was determined using the X-tile software. A total of 407 patients with ICC were selected from the analysis, including 199 cases with stage IA and 208 cases with stage IB tumors. The independent prognostic factors for patients with stage IA ICC were age and surgery. Independent prognostic factors for patients with stage IB ICC included age, surgery (yes vs. no) and tumor size (5-7 vs. ≥7 cm). The optimal cut-off value for tumor size was determined to be ~7 cm using X-tile software. Tumor size with a cut-off value of 7 cm could stratify patients by risk better than a value of 5 cm [hazard ratio (HR), 1.775; 95% confidence interval (CI), 1.356-2.323 and; HR, 1.402; 95% CI, 1.078-1.824, respectively]. This suggests that the T1 tumor category should be subclassified into T1a and T1b with a cut-off of 7 cm rather than 5 cm. The next edition of the AJCC staging system may take the present evidence into consideration for improvement regarding the accurate staging of ICC.