Validation of the American Joint Commission on Cancer (AJCC) 8th Edition Staging System for Patients with Pancreatic Adenocarcinoma: A Surveillance, Epidemiology and End Results (SEER) Analysis

The 8th edition of the AJCC staging system for pancreatic cancer incorporated several significant changes. This study sought to evaluate this staging system and assess its strengths and weaknesses relative to the 7th edition AJCC staging system. Using the Surveillance, Epidemiology and End Results (SEER) database (2004-2013), 8960 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 (c-index) were calculated to evaluate the discriminatory power of both staging systems. The Cox proportional hazards model was used to determine the impact of T and N classification on overall survival. The c-index for the AJCC 8th staging system [0.60; 95% confidence interval (CI), 0.59-0.61] was comparable with that for the 7th edition AJCC staging system (0.59; 95% CI, 0.58-0.60). Stratified analyses for each N classification system demonstrated a diminishing impact of T classification on overall survival with increasing nodal involvement. The corresponding c-indices were 0.58 (95% CI, 0.55-0.60) for N0, 0.53 (95% CI, 0.51-0.55) for N1, and 0.53 (95% CI, 0.50-0.56) for N2 classification. This is the first large-scale validation of the AJCC 8th edition staging system for pancreatic cancer. The revised system provides discrimination similar to that of the 7th-edition system. However, the 8th-edition system allows for finer stratification of patients with resected tumors according to extent of nodal involvement.