Comparison of prognoses in pancreatic cancer patients receiving neoadjuvant therapy versus adjuvant therapy.

e16451 Background: Pancreatic cancer remains one of the most lethal malignancies, with limited long-term survival despite advances in systemic therapy and surgical techniques. The optimal sequencing of chemotherapy— whether administered in the neoadjuvant or adjuvant setting—remains controversial. Comparing survival outcomes between neoadjuvant and adjuvant treatment strategies may help refine treatment algorithms and improve prognostic stratification. In this study, we aimed to evaluate overall survival outcomes by chemotherapy administration timing. Methods: This retrospective cohort study was conducted using the Surveillance, Epidemiology, and End Results (SEER) database to identify patients diagnosed with pancreatic cancer who received either neoadjuvant or adjuvant therapy between 2000 and 2022. Demographic, clinicopathological, and treatment related variables were extracted for analysis. Results: The study was analyzed using data from 5681 patients who met the study criteria. The proportion of patients aged 60 or older was higher (78.5%). Pancreatic cancer most frequently originated from the head of the pancreas (68.9%). The stage distribution of the patients included in the study at the time of diagnosis was stage 1-29.3%, stage 2-41.8%, and stage 3-28.9%, respectively. All patients had undergone primary tumor surgery. All patients had received perioperative chemotherapy, and no patient had received radiotherapy (neoadjuvant or adjuvant). The rate of patients receiving adjuvant treatment was 54.7%, while the rates of patients receiving neoadjuvant or neoadjuvant + adjuvant treatment were 25.5% and 19.8%, respectively. 1988 patients (35%) died during the follow-up period. The median survival time was 34 months (95% CI, 32.3-35.6%). 1, 3, and 5-year survival rates were 88.4%, 48.8%, and 30%, respectively. Factors affecting survival were evaluated using multivariate analysis, and the results were as follows: age (p = 0.020), gender (p = 0.535), tumor site (p = 0.071), initial stage (p < 0.001), and type of perioperative chemotherapy (p = 0.059). Overall survival was significantly better in patients receiving neoadjuvant + adjuvant chemotherapy compared to those receiving only adjuvant treatment (p = 0.024, HR: 1.14, 95% CI 1.01-1.29) or only neoadjuvant treatment (p = 0.044, HR: 1.15, 1.0- 1.32) in a one-to-one comparison. Conclusions: In this study, we evaluated the effect of optimal chemotherapy timing on overall survival in patients with operable pancreatic cancer. While the p-value for perioperative chemotherapy type was borderline in the multivariate analysis, neoadjuvant+adjuvant chemotherapy was found to be superior to either neoadjuvant or adjuvant therapy in a direct comparison. Furthermore, this study found that overall survival varied according to initial tumor stage and age at disease onset.