The effectiveness of adjuvant chemotherapy for Stage I pancreatic cancer based on the UICC 8^th edition

Background: Adjuvant chemotherapy is recommended for patients with pancreatic cancer after curative resection. However, there is limited evidence regarding the efficacy and prognostic factors for adjuvant chemotherapy in patients with stage I pancreatic cancer. This study aimed to identify patients in whom chemotherapy was effective and to detect prognostic factors for stage I pancreatic cancer based on guidelines of the 8^th edition of the Union for International Cancer Control (UICC). Methods: Between 2009 and 2017, 108 patients diagnosed with stage I pancreatic cancer were enrolled in this study. They were distributed into invasion (n = 68) and non-invasion (n = 40) groups. The relationship between clinicopathological variables, including various prognostic factors, disease-free survival (DFS), and overall survival (OS), were investigated by univariate and multivariate analyses. Results: Five-year survival in all patients with stage I pancreatic cancer was 38.9%. Adjuvant chemotherapy failed to improve DFS or OS in patients with stage I cancer (DFS, p = 0.26; OS, p = 0.30). In subgroup analysis, adjuvant chemotherapy significantly improved DFS (multivariate-adjusted hazard ratio (HR), 0.40; 95% confidence interval [CI], 0.21–0.78; p = 0.007) and OS (multivariate-adjusted HR, 0.32; 95% CI, 0.15–0.68; p = 0.003) in the invasion group than in non-invasion group. In contrast, in the non-invasion group, adjuvant chemotherapy failed to improve DFS and OS in univariate analysis (DFS, p = 0.992; OS, p = 0.808). Conclusion: For stage I pancreatic cancer, based on guidelines of the UICC 8^th edition, adjuvant chemotherapy may benefit patients with extrapancreatic invasion.