Korean nation-wide multi-institutional validation study of the 8th American Joint Commission on Cancer staging system in resected pancreatic cancer

Abstract

Introduction: The objective of this study is to validate 8th AJCC staging system using the KOTUS database. Methods: Between February, 1991 to December 2016, 1562 patients undergoing operation for pancreatic ductal adenocarcinoma were identified in KOTUS database. Among them, 159 patients with neoadjuvant therapy and 37 patients with R2 resections were excluded for analysis. Harrell's c-index was used to validate 8th AJCC staging system. Results: The Harrell's c-index was 0.591 [95% CI: 0.572-0.612] for AJCC 8th staging system and 0.571 [95% CI: 0.554-0.591] for AJCC 7th staging system. 8th staging system was not able to discriminate stage IIA with IIB (median 19 months [95% CI: 11.0-26.9] vs. median 20 months [95% CI: 17.6-22.4], p=0.945) and III (median 19 months [95% CI: 11.0-26.9] vs. median 16 months [95% CI: 14.1-17.9], p=0.128) in disease-specific survival. In 8th AJCC staging system, patients were more evenly spread among stages, whereas in 7th AJCC staging most patients were IIA (422, 31%) or IIB (859, 63%). In a subgroup analysis, patients were divided according to tumor location (head vs. body/tail) and the survival analysis showed that for both stage I (median 31 months vs. 64 months, p< 0.001) and stage II (median 18 months vs, median 42 months, p< 0.001) of AJCC 8th staging system, left-sided pancreatic cancer showed significantly better survival. Conclusions: New AJCC 8th staging system better predicts prognosis. But there are possibilities of further improvements. With results from this study, tumor location should be considered as another factor in advancing the staging system.