Validation of the eighth edition of the American Joint Committee on Cancer staging system and proposal of an improved staging system for pancreatic ductal adenocarcinoma

BACKGROUNDS/AIMS: This study aimed to validate the eighth edition of the American Joint Committee on Cancer (AJCC) staging system for pancreatic adenocarcinoma and to propose an improved staging system for this disease. METHODS: Between 2000 and 2014, 1656 patients underwent surgical resection for pancreatic ductal adenocarcinoma at Asan Medical Center, Seoul, South Korea. The 1169 patients included in this study were recategorized according to the eighth edition of the AJCC staging system. Patients were also categorized according to a new staging system, based on tumor size and number of metastatic lymph nodes. RESULTS: The seventh edition of the AJCC staging system categorized 93.7% of patients as having stage T3 tumors. Stages were distributed more evenly with the eighth edition. In the N0 group, classification according to the seventh edition showed no statistically significant differences in survival rate between patients with T1 and T2 (p=0.717) and with IA and IB (p=0.717) tumors. Survival rates classified according to the eighth edition differed significantly for all pairs of T stages (p<0.05). With both editions, N stages showed statistically significant differences (p<0.05). Reanalysis showed that a staging system using a tumor size ≥3 cm and ≥1 metastatic lymph nodes was more predictive of survival rates. CONCLUSIONS: Compared with the seventh edition, the eighth edition of the AJCC staging system for pancreatic adenocarcinoma showed a more even distribution in T stage but marginal differences in other stages. The proposed system, using tumor size and number of metastatic lymph nodes, was better at predicting survival.