Classification of pancreatic cancer: Validation using nation-wide registry of Japan pancreas society

Background and Aims: The current versions of tumor classifications for exocrine pancreas are basically based on the 2002 revisions worldwide (UICC classification Ver. 6) and in Japan (Japan Pancreas Society (JPS) classification Ver. 5). The difference of both classifications was reviewed using the JPS nation-wide pancreatic cancer registry data to validate the classifications and to propose the rational for a better classification. Patients and Methods: Records of 29817 patients with pancreatic tumor from 1981 to 2004 were collected and analyzed according to the current version of UICC and JPS classifications in terms of the decision making and prognostic indicators. Results: Locally advanced pancreatic cancers (UICC-Stage III) are less resected recent years. UICC classification is more useful in decision making while JPS classification is more predictive for survival especially in tumor 2cm or less. Histological grade are correlating with survival within a same stage of extent. Clinical progression and aggressiveness of the tumor correlates well. Both classifications are lacking the concept of early pancreatic cancer though both have Tis as carcinoma in situ. Correlation of survival rate with depth of invasion including intraductal papillary mucinous neoplasms suggests the existence of earlier lesions in pancreatic cancers. While UICC express lymph node metastasis as N0 or N1, JPS classifies as N0, N1, N2 and N3 according to the distance from the primary lesion reflecting the survival more precisely. The latest UICC-classification (7th edition) is made to include pancreatic neuroendocrine tumors, while JPS classification include every type of pancreatic exocrine, endocrine and other tumor and predicts the survival of these patients as well. Discussion: The distribution of histological classification shows that the tumor progression makes the tumor aggressiveness worse, suggesting tumor classification is not possible without knowing the origin and steps of carcinogenesis. Classifications only for invasive cancer lack the validity to precisely describe the tumor progression. Conclusion: Current versions of UICC and JPS classifications predict the survival of patients well and contribute to clinical decision making. Nation-wide pancreatic cancer registry together with follow-up data makes it possible to see the current trend of treatment, its results and collection of rare tumors including early lesions for pancreatic cancer. Both classifications should be modified to include the depth of tumor invasion to take the earlier lesions into account.