AJCC 7th edition staging classification is more applicable than AJCC 8th edition staging classification for invasive IPMN

Background Both the 7th and 8th editions of the American Joint Committee on Cancer (AJCC) staging systems have been introduced for pancreatic adenocarcinoma. However, the applicability of these classifications for invasive intraductal papillary mucinous neoplasms (IPMN) has not been systematically examined. Methods Patients with invasive IPMN were retrieved from a cohort of 18 geographical sites (1973–2014 varying) in the Surveillance, Epidemiology, and End Results (SEER) cancer registry. The 7th and 8th editions of the AJCC staging were compared. Survival rates and multivariate analyses were computed. Results In total, 1216 patients with resected invasive IPMN were included. A major difference between the 7th and 8th systems is the definition of stage IIA (7th, beyond the pancreas without involvement of major arteries; 8th, maximum tumor diameter > 4 cm). The hazard ratio (HR) of stage IIA disease (versus stage IA, HR = 2.33, P 2 cm (size > 4 cm versus > 2 ≤ 4 cm, HR = 0.91, P = 0.420). Conclusions The AJCC 7th edition staging classification is more applicable than the 8th edition classification for invasive IPMN.