Systemic Immune-Inflammation Index After Neoadjuvant Therapy Predicts the Pathological Response in Patients with Resected Pancreatic Ductal Adenocarcinoma

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) patients have improved prognosis after neoadjuvant therapy (NAT). However, there is a lack of biomarkers to predict the pathological response preoperatively. We evaluated the predictive value of multiple biomarkers, including inflammatory biomarkers, for predicting the pathological responses. Methods: We respectively reviewed the records of patients with localized PDAC who underwent NAT followed by resection between January 2017 and May 2021 at the First Affiliated Hospital of Naval Medical University. The patients were divided into the major pathological response (MPR) and non-MPR groups, according to the tumor regression grade. Univariate and multivariate predictors of MRP were explored. The predictive factors identified on multivariate analysis were used to establish a nomogram prognostic model, which was evaluated using the Decision Curve Analysis (DCA). Results: A total of 150 patients, including 21 in the MPR and 129 in the non-MPR group, were analyzed. In the multivariate analysis of the MRP group, normal CA19-9 level (<37U/ml)(odds ratio, OR = 32.014; 95% confidence interval (CI) = 3.809–269.071; p = 0.001), post-NAT SII < 530 (OR = 14.739; 95% CI = 2.811–77.265; p = 0.001), and use of Stereotactic Body Radiation Therapy (OR = 8.370; 95% CI = 2.175–32.205) predicted MPR in PDAC patients. DCA showed that the nomogram prognostic model had a higher predictive value than standard radiological assessments. Conclusions: In resected PDAC, post-NAT normal CA19-9 level, post-NAT SII, and use of Stereotactic Body Radiation Therapy predicted MPR after NAT in PDAC patients. Post-NAT SII can be used as a biomarker to determine the treatment response.