Modification of the 8th AJCC staging system of pancreatic ductal adenocarcinoma
Accurate cancer staging is critical not only for planning the clinical management, but also for predicting prognosis in patients with pancreatic ductal adenocarcinoma (PDAC). The former American Joint Committee on Cancer (AJCC) staging system (7th edition) for PDAC has failed to show prognostic relevance of T stage since vast majority (>90%) of patients who underwent pancreatectomy were classified as T3 (1,2). Moreover, the definition of T3 as tumor extension beyond pancreas without involvement of the celiac axis or superior mesenteric artery (SMA) gave rise to significant inter-observer/institutional variability due to lack of true capsule in the pancreas and highly variable distribution of adipose tissue surrounding the pancreatic parenchyma. To address these issues, the current AJCC staging system for PDAC (8th edition) uses only tumor size for T1 to T3 (T1, ≤2 cm; T2, >2 cm and ≤4 cm; T3, >4 cm), but maintains the T4 definition as tumor of any size involving the celiac axis, SMA and/or common hepatic artery. The current AJCC staging also subclassifies lymph node (LN) positive group into N1 (1–3 positive LNs) and N2 (≥4 positive LNs). The current 8th AJCC staging system allows for better reproducibility for T stage classification and better patient stratification compared to AJCC 7th edition (1).