Evaluation and Recommendation of the 8th Edition of American Joint Committee on Cancer (AJCC) Staging System for Intrahepatic Cholangiocarcinoma (ICC) in 820 Patients from the Surveillance, Epidemiology, and End Results (SEER) Database.

Background: The AJCC made four changes to T category in the 8th AJCC stage for ICC, but this is a topic of debate.
Methods: Data from 820 patients with ICC were extracted from the SEER database. Survival analysis of the 8th AJCC stage was examined.
Results: To verify the four T staging changes by survival analysis: prognosis of patients with tumor size > 5 cm was poorer than that with tumor size ≤ 5 cm (P < 0.05); in N0M0 cohort, there was no significant difference in survival between solitary tumor with vascular invasion and multiple tumors (P = 0.092), tumor perforating the visceral peritoneum with and without involving local extrahepatic structures by direct invasion (P = 0.470), and tumor with and without periductal invasion (PI) (P = 0.220). The prognosis of patients with ≥ 4 positive lymph nodes was relatively poor compared with 1-3 positive lymph nodes (P = 0.037) and similar to patients with stage IV (8th AJCC, P = 0.585).
Conclusion: This study found that there was no significant difference in survival between tumor perforating the visceral peritoneum with and without involving local extrahepatic structures by direct invasion, whereas other T staging changes were effective. The inclusion of the number of positive lymph nodes in the 8th AJCC stage may improve prognostic discrimination in ICC patients.