Refining the American Joint Committee on Cancer Staging Scheme For Resectable Pancreatic Ductal Adenocarcinoma Using Recursive Partitioning Analysis

Purpose: It remains unclear whether the recently proposed 8^th edition of the American Joint Committee on Cancer (AJCC) staging scheme for pancreatic ductal adenocarcinoma (PDAC) outperforms the 7^th edition. We assessed the prognostic performance of both these schemes and performed recursive partitioning analysis (RPA) to objectively regroup the 7^th and 8^th AJCC stages and derive a refined staging scheme. Methods: We examined 8542 patients with resectable PDAC from the 2004-2012 Surveillance, Epidemiology, and End Results database. The dataset was randomly divided into training and validation sets. The performance of different staging schemes was evaluated in terms of prognostic stratification, discriminatory ability, and prognostic homogeneity. Results: The 7^th and 8^th T classifications showed prominent heterogeneity within each subcategory when assessed against each other in the case of node-negative disease. RPA divided resectable PDAC into RPA-IA (8^th T1N0 limited to the pancreas), RPA-IB (8^th T1N0 extending beyond the pancreas, or 8^th T2-T3N0 limited to the pancreas), RPA-IIA (8^th T2N0 extending beyond the pancreas, or 8^th T1N1-N2), RPA-IIB (8^th T3N0 extending beyond the pancreas, or 8^th T2-T3N1), and RPA-III stages (8^th T2-T3N2) (median survival in the training set: 47, 28, 20, 16, and 14 months, respectively; P < 0.001). The RPA staging scheme outperformed the 7^th and 8^th AJCC classifications in terms of prognostic stratification, discriminatory ability, and prognostic homogeneity for both the training and validation sets. Conclusions: The proposed RPA staging is a superior risk-stratified tool to the 7^th and 8^th AJCC classifications and is not substantially more complex.