Background: Although lymph node metastasis (LNM) is an important prognostic indicator for patients with intrahepatic cholangiocarcinoma (ICC), the benefit and indication for lymphadenectomy remain unclear. Methods: Patients diagnosed with ICC between 1990 and 2016 were identified in the international multi-institutional dataset. To determine the survival benefit from lymphadenectomy, the therapeutic index was calculated by multiplying the frequency of LNM in a particular group of patients by the 3-year cancer-specific survival (CSS) rate of patients with LNM in that subgroup. Results: Among 471 patients who met the inclusion criteria, approximately half had LNM (n = 205, 43.5%). The median number of resected and metastatic LNs were 4 [interquartile range (IQR) 2–8] and 0 (IQR 0–1), respectively. Three-year CSS in the entire cohort was 29.9%, reflecting a therapeutic index value of 13.0. The therapeutic index was lower among patients with major vascular invasion (5.4), preoperative carcinoembryonic antigen (CEA) > 5.0 (8.2), and LNM in areas other than the hepatoduodenal ligament (5.2). Of note, a therapeutic index difference of more than 10 points was noted only when examining the number of LNs harvested [1–2 (4.1) vs. 3–6 (16.1) vs. ≥ 7 (17.8)]. Conclusion: The survival benefit derived from lymphadenectomy was poor among patients with major vascular invasion, CEA > 5.0, and LNM in areas other than the hepatoduodenal ligament. Resection of three or more LNs was associated with the highest therapeutic value among patients with LNM.
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