E262: Prognostic Significance of Lymph Node Ratio in Intrahepatic and Extrahepatic Cholangiocarcinomas

Introduction: Lymph Node Ratio (LNR) has previously shown promising prognostic potential in various cancer types. This study aims to assess the impact of LNR on survival in patients undergoing surgical resection for intrahepatic (ICC) and extrahepatic (ECC) cholangiocarcinoma.

Methods: A retrospective analysis of the National Cancer Database from 2004 to 2020 was conducted. We included patients with topography codes C22.1 and C24.0 and histology codes 8140, 8160, and 8162, consistent with ICC and ECC. Site-specific codes for distal bile duct cancer were excluded. Adult patients ( >18 years) who had primary site resection with adequate lymphadenectomy (≥4 LNs excised) were eligible. Exclusions comprised distant metastasis or incomplete data for staging, follow-up, and adjuvant chemotherapy. LNR was calculated as the ratio of positive LNs to total examined LNs. Kaplan-Meier Survival Analysis estimated survival probabilities, Hazard Ratios (HRs) were calculated using Cox Regression analysis.

Results: Inclusion criteria were met by 2,561 patients, with 954 having ICC and 1,607 with ECC. The average age was 65.39 years (± 11.3), with 56.8% males and 81.6% identifying as white. Most cases (65.6%) were diagnosed with AJCC stages II and III disease. Overall survival (OS) was 44.2 vs 38 months for ICC and ECC, respectively.
Patients were stratified into the following LNR groups by primary site: negative LN, LNR< 0.3 and LNR≥0.3. The mean overall survival (fig. 1) was 49.6 and 46.2 months in the negative LN group, 39.4 and 33.3 months in LNR < 0.3, 31.8 and 26.1 months in LNR ≥0.3 for ICC and ECC respectively (difference significant, p< .001). The 3-year survival for ICC was 69.3% in negative LN, 55.5% in LNR < 0.3, 34% in LNR ≥0.3; for ECC 64.7% in negative LN, 42.7% in LNR < 0.3, and 27.3% in LNR ≥0.3 (p< .05). The difference in survival persisted when adjusted for adjuvant chemotherapy and surgical margins using Cox regression, HR 2.1 in LNR < 0.3 for both ICC and ECC, HR 2.9 and 3 in LNR ≥0.3 for ICC and ECC, respectively (p< .001). In the same model, HR was 1.5 for both ICC and ECC in LNR≥0.3 when compared to LNR < 0.3 (p< .001).

Conclusions: This study suggests LNR is a valuable prognostic factor for ICC and ECC patients with potential significance in predicting survival outcomes and guiding treatment strategies.