Gross tumor size using the AJCC 8th ed. T staging criteria does not provide prognostic stratification for neoadjuvant treated pancreatic ductal adenocarcinoma

Abstract

The 8th edition AJCC T stage criteria for pancreatic ductal adenocarcinoma (PDAC) are now size based. These criteria provide better prognostic stratification in patients without neoadjuvant therapy. Our aim was to determine if gross tumor size is prognostically significant using the 8th ed. staging criteria for neoadjuvant treated PDAC. The study included 289 patients who underwent resection for PDAC following neoadjuvant therapy. By AJCC 7th ed., there were 12 (4.2%) ypT0, 32 (11.1%) ypT1, 64 (22.1%) ypT2, and 181 (62.6%) ypT3 patients. By AJCC 8th ed., there were 12 (4.2%) ypT0, 74 (25.6%) ypT1 (6 ypT1a, 1 ypT1b, 67 ypT1c), 161 (55.7%) ypT2, and 42 (14.5%) ypT3 patients. 182 patients had negative lymph nodes and 107 had positive lymph nodes. 77 patients were ypN1 and 30 were ypN2 by 8th ed. criteria. 7th ed. T stage significantly correlated with OS (p = 0.048), while 8th ed. T stage did not correlate with OS (p = 0.13). In ypN0 patients, neither the 7th ed. or 8th ed. T stages significantly correlated with patient OS (p = 0.065 and 0.26, respectively). Higher 7th ed. T stage correlated with lymph node status (p ≤ 0.001) more strongly than 8th ed. T stage (p = 0.04). 7th ed. and 8th ed. N stage correlated with OS (p = 0.004 and p = 0.0002, respectively). By 8th ed. AJCC staging criteria, gross tumor size does not provide good prognostic stratification in neoadjuvant therapy PDAC. Mapped grossing techniques combining gross and microscopic examination to determine tumor size may provide more accurate staging of neoadjuvant treated tumors.