High Systemic Immune-Inflammation Index Values Before Treatment Predict Poor Pancreatic Cancer Outcomes After Definitive Chemoradiotherapy

Background: The systemic immune-inflammation index (SII) is an effective tool for predicting the prognosis of patients with cancer. However, its value in patients with locally advanced pancreatic ductal adenocarcinoma (LA-PDAC) undergoing definitive chemoradiotherapy has yet to be addressed. Therefore, we aimed to retrospectively investigate the prognostic significance of the pretreatment SII on the survival outcomes of patients with unresectable LA-PDAC treated with concurrent chemoradiotherapy (C-CRT).

Methods: The study included 163 patients with LA-PDAC who had received C-CRT. Using receiver operating characteristic (ROC) curve analysis, the utility of a pre-C-CRT cutoff that could stratify survival results was investigated. The primary and secondary endpoints were the correlations between SII levels and overall survival (OS) and progression-free survival (PFS).

Results: At a median follow-up period of 15 months (range: 3.2-94.5), the median OS and PFS rates for the entire group were 15.7 months (95% confidence interval [CI]: 13.4-17.9), and 7.8 months (95% CI: 6.1-9.4), respectively. We divided the patients into 2 SII cohorts based on the ROC curve analysis (area under the curve [AUC]: 71.9%; sensitivity: 68.9%; specificity: 66.7%): SII < 538 (N = 70) and SII ⩾ 538 (N = 93). Comparative survival analysis showed significantly inferior median OS (13.0 vs 25.4 months; P < .001) and PFS (7.0 vs 15.2 months; P = .003) in patients with SII ⩾ 538 compared with those with SII < 538 before treatment. In multivariate analyses, the Eastern Cooperative Oncology Group (ECOG) performance of 2, N1-2 lymph node, CA 19-9 > 90 U/mL, and SII ⩾ 538 status emerged as independent prognosticators of inferior OS and PFS.

Conclusions: Present results indicate that patients with unresectable LA-PDAC who underwent C-CRT and had a pretreatment SII ⩾ 538 had significantly worse OS and PFS outcomes compared with those with lower SII values.