Preoperative Systemic Immune-Inflammatory Index Predicts Occult Nodal Disease in Clinically Node-Negative Intrahepatic Cholangiocarcinoma.

Background: Accurate preoperative diagnosis of nodal status in intrahepatic cholangiocarcinoma (ICC) remains challenging. The objective of the current study was to determine if the systemic immune-inflammatory index (SII) was associated with occult nodal disease (OND) among cN0 patients undergoing resection for ICC.

Methods: Patients who underwent curative resection for ICC were identified from an international multi-institutional database. A multivariable logistic regression model was used to assess the relationship between SII and OND.

Results: Among 490 patients who underwent curative resection with lymph node dissection (LND) for cN0 ICC, 135 (27.6%) had OND. Among these individuals, high SII (≥738.4) was independently associated with OND (odds ratio [OR], 1.85, 95% confidence interval [CI], 1.18-2.92). This association was consistent even among patients with cT1aN0M0 disease (OR, 1.85; 95% CI, 1.19-2.88). Interestingly, among patients with high SII and N0/Nx disease, individuals whose total number of lymph nodes examined (TLNE) was fewer than six had worse 3-year recurrence-free survival (RFS) than patients with a TLNE of six or more (38.8% vs 74.0%; p = 0.002). In contrast, RFS did not differ among patients with low SII and N0/Nx disease (TLNE <6 [49.1%] vs ≥6 [62.4%]; p = 0.099).

Conclusions: High SII was an independent predictor of OND, even among patients with early-stage disease, suggesting that incorporating SII into preoperative risk assessment may refine staging and guide treatment strategies including the need for neoadjuvant therapy as well as the extent and adequacy of LND.