Background: Lymph node metastasis is an important prognostic factor for distal bile duct cancer. The number of lymph node metastases was adopted for nodal classification. However, different cutoff values have been proposed, ranging from two to five. Methods: A total of 1748 cases who underwent curative surgery with pancreatoduodenectomy for distal bile duct cancer registered in the nationwide biliary tract cancer registry in Japan from 2008 to 2013 were included. Univariate Cox regression was performed to assess the effect of prognostic lymph node metastasis counts on mortality and to determine cutoff values. Results: The overall survival rate after resection was 47.4% at 5 years. Univariate and multivariate analysis found prognostic factors to include lymph node metastasis. The cutoff point was set to two lymph node metastases using the Cox model. There were significant differences in pairwise comparisons between three groups by the number of metastatic lymph node (P <.001 for 0 vs 1-2 and P =.003 for 1–2 vs ≥3). Conclusion: Our data suggest lymph node classification as N0 (patients without lymph node metastases), N1 (metastasis in 1–2 regional lymph nodes), and N2 (metastases in ≥3 regional lymph nodes).
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