Introduction : We validated 7th and 8th AJCC staging system. Second, we tried to find the optimal value for T category, total lymph node count (TLNC), positive lymph node count (PLNC) and lymph node ratio (LNR). Finally, comparison of performance by various staging models was performed.

Methods : We retrospectively reviewed 251 patients who underwent surgery for DCC at 4 centers. To determine optimal cutoff value, univariate and multivariate Cox regression analyses were used and χ2 score of each values were compared. To compare the predictive superiority of various staging models, Akaike information criterion (AIC), Bayesian information criterion (BIC), AIC correction (AICc), and Harrells C-statistic were calculated.

Results : When applying the optimal cut off value for T category, the categories are classified as follows and referred to as ‘revised T category’: T1 (<5mm), T2 (5-10mm) and T3(>10mm). As to N category, PLNC is divided into N (0), N (1-2) and N (≥ 3). LNR were divided into 3 groups (0, >0 to <0.1 and ≥0.1). In multivariate analysis, age (P = 0.003), TLNC (P = 0.033), revised T(LNR)M staging (P < 0.001) were identified as independent factor for OSR. The predictive performance of revised T (LNR) M staging (AIC:1288.925, BIC 1303.377, AICc 1291.52 and Harrell’s C statics 0.667) was superior to other staging system.

Conclusions : A modified staging system consisting of revised T category and LNR predicted better overall survival of DCC than AJCC 7th and AJCC 8th editions.