Chemotherapy progression decision score to improve subsequent treatment regimen selection after initial assessment for pancreatic ductal adenocarcinoma.

e16388 Background: This study aims to develop a chemotherapy progression decision (cPD) score for pancreatic ductal adenocarcinoma (PDAC), designed as a clinically accessible tool in determining the keep or alteration of therapeutic strategies for patients exhibiting stable or progressive disease at initial assessment using the Response Evaluation Criteria in Solid Tumors (RECIST). Methods: This retrospective study included a training set of 155 patients receiving chemotherapy for PDAC at the Second Affiliated Hospital of Zhejiang University School of Medicine (SAHZU cohort) between 1 January 2016 and 31 December 2023.Validation set including four hospitals in Zhejiang Province of 263 patients(validation one cohort) and 198 patients in the China Pancreas Data Center (CPDC cohort). Clinical, radiological and biological data at baseline and first evaluation were analyzed. Performed univariate and multivariate analysis of factors associated with overall survival (OS). cPD score was developed based on the multivariate hazard ratios (HR) of all significant predictors. Patients were stratified into three groups: Good Prognosis (GP), Poor Prognosis (PP) and Critical Prognosis (CP) according to cPD score using x-tile software. Subgroup survival analyses were performed for each group in relation to the keep or alteration of therapeutic strategies after initial assessment in the SAHZU and validation set one cohorts. Kaplan-Meier analyse and log-rank tests were used to calculate OS for each group. Results: Multivariate analysis identified several independent prognostic factors which were incorporated into the cPD score: Neutrophil-to-Lymphocyte Ratio (NLR), Carbohydrate Antigen 19-9 (CA19-9), percentage of tumor shrinkage and the emergence of new lesions. These variables were each recognized as adverse survival factors. Patients were assigned scores based on the HR for each factor categorized into GP, PP, and CP based on cPD scores ranging from 12-13, 10-11, to 8-9, respectively. Three groups showed significantly different survivals (GP: 12.20, PP: 8.87, CP: 6.27 months median OS, p < 0.001). The median survival for each group is 13.70, 9.40, 5.43 months in the validation one cohort and 18.93, 15.27, 8.60 in the CPDC cohort. Survival of GP and PP patients who changed treatment regimens was shorter than that of those who did not, but there was no significant difference in survival of CP patients regardless of treatment change. Conclusions: The cPD score offers a novel post-chemotherapy assessment metric for PDAC to decide if treatment should be continued (for the GP group), or immediately changed for the CP groups. Patients in the PP group are recommended remain on their original chemotherapy regimen, but with a shorter interval for subsequent efficacy assessments. Further validation on larger cohorts is needed to prove its efficacy in clinical practice. Univariate and multivariate cox proportional hazards regression analysis of factors (after -tile calculation) associated with overall survival. Factors Univariate Multivariate HR (95% CI) P HR (95% CI) P NLR >3.4 2.140(1.512,3.027) 0.00 0 1.906(1.325,2.742) 0.001 Baseline CA19-9 level>2000 1.980(1.407,2.785) 0.000 1.501(1.037,2.171) 0.031 Tumor maximum cross-sectional rate change ratio<-0.1(long diameter*short diameter) 1.608(1.132,2.286) 0.008 1.491(1.043,2.132) 0.028 Emergence of new lesions 1.958(1.381-2.776) 0.000 1.722(1.185,2.503) 0.004 HR, hazard ratio; NLR,Neutrophil-to-Lymphocyte Ratio.