Is the New T1 Category as Defined in the Eighth Edition of the AJCC Pancreatic Cancer Staging System an Improvement?

Background The new T1 pancreatic cancer by the eighth edition of the AJCC staging system discards the concept of “extension beyond the pancreas” and focuses on size only. Furthermore, the new T1 is divided into T1a, T1b, and T1c based on size. The evidence pertaining to these changes has not been evaluated. This is to evaluate the feasibility of the new T1 definition in the pancreas head cancer cohort. Methods Data from 540 patients with T1 pancreatic ductal adenocarcinoma as defined by the eighth edition were collected from Korea, Japan, and the USA. Invasive IPMNs were excluded. Survival analyses were performed. Results Of the 540 patients, 181 patients were T1 according to the seventh edition and 359 were down-staged to T1 from the former T3 because the concept of “extension beyond the pancreas” was discarded. The 5-year survival rate and the median survival of T1 patients were 30.6% and 27 months, respectively. Comparing tumors that extend beyond the pancreas (new T1) and those confined within the pancreas (original T1), the latter showed significantly longer median survival (43 vs. 24 months, p