Systemic immune-inflammation index as a prognostic marker for distal cholangiocarcinoma.

PURPOSE The systemic immune-inflammation index (SII) is a new marker, defined as the platelet count × neutrophil-to-lymphocyte ratio. This study evaluates the SII as a prognostic marker for the overall survival (OS) of patients who underwent pancreatoduodenectomy (PD) for distal cholangiocarcinoma (DCC). METHODS One hundred and forty patients who underwent PD for DCC between September, 2002 and December, 2015 at our hospital were divided into a low SII (SII < 1450) group and a high SII (SII ≥ 1450) group. We compared the clinicopathological characteristics and OS of the two groups retrospectively and used multivariate analyses to identify the prognostic factors for OS. RESULTS The low and high SII groups comprised 119 and 21 patients, respectively. OS was better in the low SII group than in the high SII group, with median survival times of 81 and 26 months, respectively (p < 0.001). Multivariate analyses revealed that portal vein resection (hazard ratio [HR], 9.58; p < 0.001), SII ≥ 1450 (HR, 2.05; p = 0.041), microscopic venous invasion (HR, 2.04; p = 0.005), and pN1 (HR, 1.73; p = 0.034) were independently associated with poor survival. CONCLUSION The SII may be useful for predicting the long-term survival of patients with DCC after PD.