The Prognostic Importance of the Number of Metastatic Lymph Nodes for Patients Undergoing Curative Resection Followed by Adjuvant Chemoradiotherapy for Extrahepatic Bile Duct Cancer

Background: Current nodal staging system for extrahepatic bile duct (EHBD) cancer is controversial. The number of metastatic lymph nodes (mLN) and lymph node ratio (LNR) has been studied for the assessment of the nodal status in many other gastrointestinal cancers, but there are few studies on assessing the prognostic impact of these parameters in EHBD cancer. Methods: We retrospectively reviewed 239 consecutive patients who underwent curative resection followed by adjuvant chemoradiotherapy for adenocarcinoma of EHBD from 1995 to 2009 in our institution. The prognostic value of the number of mLN and LNR was evaluated by adjusting for other known factors. Optimal cutoff points were determined using maximally selected chi-square test. Results: Lymph node metastasis was found in 77 (32 %) patients. Univariate analysis for overall survival (OS) revealed both the number of mLN (0 vs. 1–3 vs. ≥4; p < 0.001) and LNR (<0.2 vs. ≥0.2; p < 0.001) as significant prognosticators. Multivariate analysis demonstrated that the number of mLN was an independent prognostic factor, whereas LNR was not. The estimated 5-year OS was 48.7 % for patients with negative nodes, 33.4 % for patients with 1–3 mLN, and 9.1 % for patients with 4 or more mLN (p < 0.001). Conclusions: The number of mLN is a powerful parameter to predict survival in the EHBD cancer, which is more reliable than LNR. As for many other gastrointestinal cancers, further classification of node positive patients based on the number of mLN seems to be useful and may provide precise information.