Neoadjuvant Treatment with Changes in Chemotherapy Regimens According to Carbohydrate Antigen 19-9 Level for Resectable/Borderline Resectable Pancreatic Ductal Adenocarcinoma.

Background: The response of carbohydrate antigen (CA) 19-9 to neoadjuvant therapy (NAT) for pancreatic ductal adenocarcinoma (PDAC) may contribute to outcomes. This study aimed to investigate the effect of changes in NAT regimens based on CA19-9 level.

Methods: This single-center retrospective study included patients with resectable/borderline resectable (R/BR)-PDAC undergoing NAT from 2008 to 2022. A CA19-9 level lower than 150 IU/mL after NAT was the criterion for resection. If the level did not decrease, the chemotherapy regimen was changed to satisfy the criterion. The patient cohort was divided into group A (satisfied criterion without changing chemotherapy), group B (did not receive chemotherapy change, could not satisfy the criterion), group C (received chemotherapy change, satisfied the criterion), and group D (received chemotherapy change, could not satisfy the criterion).

Results: The study cohort included 283 patients. After first-line chemotherapy, 112 (39.6%) patients did not satisfy the criterion (groups B [n = 64], C [n = 32], and D [n = 16]). Of the 283 patients, 48 (17%) received a chemotherapy change (groups C and D). The patients in groups C and D showed significantly better overall survival (OS, 35.9 months) than the group B patients (25.7 months) (P = 0.035). The OS of the group C patients (63.8 months) was similar to the OS of the group A patients (n = 171: 56.3 months; P = 0.430). Multivariate analysis of the patients in groups B, C, and D identified chemotherapy change as an independent prognostic factor for OS and progression-free survival.

Conclusion: Changing the chemotherapy targeting the CA19-9 level can improve the outcome of R/BR-PDAC patients with poor biologic response to first-line NAT.