Radial Margin Distance in Perihilar Cholangiocarcinoma

OBJECTIVE: To evaluate the prognostic impact of radial margin distance (RMD) in patients with perihilar cholangiocarcinoma (pCCA) and establish clinically relevant cutoff values. BACKGROUND: A positive radial margin is conventionally defined by cancer cell exposure at the transection plane. However, a standardized classification for pCCA has yet to be established. METHODS: pCCA patients who underwent tumor resection between 2005 and 2020 were retrospectively analyzed. The relationships between histologically measured RMDs and long-term outcomes were examined. RESULTS: Among the 658 study patients, the median RMD was 0.4 mm (interquartile range, 0.1-1.1 mm). The hazard for overall survival peaked at an RMD of 0 mm (conventional cutoff), decreased with increasing RMD, and plateaued at approximately 1.0 mm, which was identified as the optimal threshold in rank statistics (|z|, 11.09; P<0.001). On the basis of these findings, patients were categorized into three groups according to their RMDs (0 mm (n=101, 15.3%), >0-<1.0 mm (n=356, 54.1%), and ≥1.0 mm (n=201, 30.5%)); the 5-year cumulative recurrence rates were 83.5%, 68.8%, and 23.9%, respectively (P<0.001), with local recurrence rates of 63.0%, 37.0%, and 11.1%, respectively (P<0.001), and the 5-year overall survival rates were 21.8%, 36.0%, and 78.5%, respectively (P<0.001). Multivariable analysis confirmed that RMDs of 0 mm (hazard ratio, 3.15; P<0.001) and >0-<1.0 mm (hazard ratio, 2.64; P<0.001) were independent predictors of poor overall survival. CONCLUSIONS: RMD assessment with dual cutoffs of 0 and 1.0 mm was simple and clinically relevant and effectively stratified postoperative recurrence risk and survival in pCCA patients.