Carbohydrate Antigen 19-9 Delta Function for Survival Prediction in Borderline Pancreatic Cancer. A PANC-PALS Consortium International Multicenter Derivation and Validation Study.

OBJECTIVE To establish a novel method for evaluating carbohydrate antigen 19-9 (CA19-9) during neoadjuvant therapy (NAT) and assess its role in predicting overall (OS) and disease-free (DFS) survival in borderline resectable pancreatic adenocarcinoma (BR-PC). SUMMARY BACKGROUND DATA Static CA19-9 values or percentage changes often fail to capture therapeutic responses in patients with BR-PC undergoing NAT. Improved evaluation methods are essential for guiding the treatment. METHODS This was a retrospective multicenter study of patients who underwent BR-PC surgery. Two parameters were developed: slope coefficient (SC, change in CA19-9 divided by therapy duration) and mean δf (mδf, calculated as the sum of CA19-9 values over therapy intervals divided by the number of 15-day periods). The main objective was to correlate mδf with OS thresholds derived using a maximally selected log-rank statistic and validated in independent cohorts. RESULTS Overall, 991 patients (median age 65 [59-71] years; 49% male) were included. The thresholds for mδf were defined as U.mL-1. month-1 (negative SC) and U.mL-1. month-1 (positive SC). Patients with mδf below these thresholds had significantly better prognoses, with hazard ratios (HR) for OS (95% CI) of 0.6 (0.4-0.8; P<0.01) and 0.4 (0.2-0.9; P=0.04) for negative and positive SC, respectively. Both thresholds were validated for mOS, with 29 vs 22 months (P=0.015) and 32 vs 16 months (P=0.0034) for negative and positive SC, respectively. Similarly, the mDFS was 13 vs 10 months (P=0.011) and 12 vs 7 months (P=0.0018), respectively. CONCLUSION This CA19-9 evaluation approach accurately predicts survival outcomes, offering a valuable tool for optimizing treatment strategies. An mδf calculator is available at https://www.pancpals.com/tools.