Efficacy of Adjuvant Chemotherapy According to the Pathological Response to Neoadjuvant Chemotherapy Among Patients With Pancreatic Ductal Adenocarcinoma

Background/Aim: An association between the pathological response to neoadjuvant chemotherapy (NAC) and the efficacy of adjuvant chemotherapy (AC) in patients with pancreatic ductal adenocarcinoma (PDAC) remains unknown. Patients and Methods: A total of 121 patients with PDAC who underwent a pancreatectomy between January 2013 and March 2020 were divided into two groups: an upfront surgery (UFS) group (n=42), and an NAC (gemcitabine plus S-1) group (n=79). In the NAC group, the pathological response was evaluated using the Evans classification. Results: The overall survival was significantly higher in patients with an AC relative dose intensity (RDI) ?80% than in patients with an AC RDI <80% in the UFS, NAC-Evans IIa, and NAC-Evans IIb+III groups. However, this difference was not observed in the NAC-Evans I group. Conclusion: AC is preferable for patients with NAC-Evans IIa or IIb+III, but more effective AC regimens may be needed for NAC-Evans I patients.