Perineural invasion as a prognostic factor for intrahepatic cholangiocarcinoma after curative resection and a potential indication for postoperative chemotherapy: a retrospective cohort study

BACKGROUND: In the past four decades, the incidence of cholangiocarcinoma, especially intrahepatic cholangiocarcinoma (ICC), has raised rapidly worldwide. Completeness of resection, max size of tumor and etc. are widely recognized as prognostic factors. However, the prognosis significance of perineural invasion (PNI) on recurrence-free survival (RFS) and overall survival (OS) in ICC patients is controversial. METHODS: ICC patients who underwent curative hepatectomy and diagnosed pathologically were retrospectively analyzed. Patients were grouped by existence of PNI and outcomes were compared between groups. The potential relationship between PNI and postoperative chemotherapy was also investigated. RESULTS: There was no significant difference in demographic, clinical staging or tumor index between two groups, except positive hepatitis B surface antigen and CA19–9. PNI negative group showed a better prognosis in RFS (P < 0.0001) and OS (P < 0.0001). COX regression analyses showed PNI as an independent risk factor in RFS and OS. ICC with postoperative chemotherapy showed better effects in the whole cohort on both RFS (P = 0.0023) and OS (P = 0.0011). In PNI negative group, postoperative chemotherapy also showed significant benefits on RFS and OS, however not in PNI positive group (P = 0.4920 in RFS and P = 0.8004 in OS). CONCLUSION: PNI was an independent risk factor in R0-resected ICC, presenting worse recurrence and survival outcomes. Meanwhile, negative PNI may act as an indication of postoperative chemotherapy.