Evaluation of the 8th Edition AJCC Staging System for the Clinical Staging of Pancreatic Cancer

SIMPLE SUMMARY: The 8th edition of the AJCC staging system for pancreatic cancer has been validated for pathological staging; however, its suitability for clinical staging is still uncertain. Clinical staging is important for pancreatic cancer because surgical resection is not suitable for most patients. We validated the prognostic performance and suitability of the current staging system for clinical staging. In our analysis using a prospectively collected pancreatic cancer cohort database, survival difference was not shown between stage IB and IIA, which were divided by the new size-based T3 criterion. Among the patients who received surgery, the pathological stage was more advanced than the clinical stage in 57.3%, mostly due to a false-negative lymph node in clinical staging. These findings suggest that the 8th edition AJCC staging system is not validated for clinical staging and separate criteria more suitable for clinical staging should be established. ABSTRACT: The 8th edition of the American Joint Committee on Cancer (AJCC) staging system for pancreatic cancer (PC) has been validated for pathological staging; however, its significance for clinical staging remains uncertain. We validated the prognostic performance and suitability of the current staging system for the clinical staging of PC. We identified 1043 patients from our PC registry who were staged by imaging according to the 8th edition staging system and conducted analysis, including overall survival (OS) comparison. Gradual prognostic stratification according to stage hierarchy yielded significant OS differences between stage groups, except between stage I and II (p = 0.193). A substage comparison revealed no survival differences between IB (T2N0) and IIA (T3N0), which were divided by the T3 criterion only (p = 0.278). A higher N stage had significantly shorter OS than a lower N stage (all pairwise p < 0.05). However, among the 150 patients who received upfront surgery, the pathological stage was more advanced than the clinical stage in 86 (57.3%), mostly due to a false-negative cN0 (70.9%). Our results suggest that the new definition of T3 and the number-based N criteria in the 8th edition AJCC staging system may be not adequate for clinical staging. Establishing separate criteria more suitable for clinical staging should be considered.