Background: The 8th edition AJCC staging system for pancreatic cancer incorporated several significant changes. We sought to evaluate this staging system and assess its strengths and weaknesses relative to the 7th edition system. Methods: Using the Surveillance, Epidemiology and End Results (SEER) database (2004-2013), 8,960 patients undergoing surgical resection for non-metastatic pancreatic adenocarcinoma were identified. Overall survival was estimated using the Kaplan-Meier method and compared using log-rank tests. Concordance indices were calculated to evaluate the discriminatory power of both staging systems. Cox proportional hazards model were used to determine the impact of T and N classification on overall survival. Results: The concordance index for AJCC 8th staging system (0.60,CI95% 0.59-0.61) was comparable to that for the 7th AJCC staging system (0.59,CI95% 0.58-0.60). Stratified analyses for each N classification system demonstrated diminishing impact of T classification on overall survival with increasing nodal involvement. The corresponding concordance index for N0, N1 and N2 classifications were 0.58 (CI95%:0.55-0.60), 0.53 (CI95%:0.51-0.55), and 0.53 (CI95%:0.50-0.56) respectively. Conclusion: This is the first large-scale validation of the AJCC 8th edition staging system for pancreatic cancer. The revised system provides similar discrimination as compared to the 7th edition system. However, the 8th edition system allows finer stratification of patients with resected tumors according to extent of nodal involvement.

activated. We also found that the MHC II antigen presenting pathway is downregulated in tumors. Conclusion: This study has showed that immune response is activated during PDAC, however, several evading mechanisms were simultaneously observed. Although the immune system might be activated, these mechanisms may ensure tumour cells avoid being recognized and subsequently eliminated. Thus, targeting these mechanisms might prove beneficial for the development of immunebased therapeutic strategies for PDAC treatment.Caption 1: Simultaneous enrichment of immune and signalling pathways in early pancreatic ductal adenocarcinoma patients.