Japanese Pancreas Society Staging Systems for Pancreatic Cancer
Both Japan Pancreas Society (JPS) staging system and International Union Against Cancer (UICC) staging system adopt TNM classification, however, there are considerable differences in detail. Regarding the T category, a tumor involving only the intrapancreatic bile duct is classified as UICC T1 or T2 tumor, but as JPS T3. Most of resectable tumors are altogether classified into UICC T3, however, into JPS T3 or T4. Invasion to extrapancreatic nerve plexus (PL) is treated as JPS T4, but as UICC T3. Since massive perineural invasion to PL around the major artery often causes encasement of the artery, it might be recommended in the future revision that UICC T4 definition should be interpreted as “Tumor involves CA, SMA, or PL around these arteries.” The N category in the UICC staging system is quite simple as N0 or N1 indicating positive regional nodes. In the JPS staging system, N1; N2; and N3 correspond to metastasis to lymph nodes that are unintendedly removed altogether with the pancreas during pancreatoduodenectomy or distal pancreatectomy; regional nodes that are resected with intent of curative lymphadenectomy; and distant lymph nodes that are rarely included for curative lymphadenectomy, respectively.
The JPS stage grouping is adequate for analysis of patient population treated with surgical resection. Stages of resected cases would be dispersed from stage I to IVb. Non-resected cases would be concentrated into stage IVb and partly classified into stage IVa. On the other hand, the UICC stage grouping is suitable to include both resected and non-resected cases. Stages of resected cases would be dispersed from stage IA to IIB with slight concentration to stage IIB that corresponds to regional/nodal disease. Stages of non-resected cases would be divided into stage III corresponding to locally far advanced disease and stage IV corresponding to metastatic/systemic disease. A clinical review of the staging systems using data from National Pancreatic Cancer Registry in Japan showed that the JPS staging system proved its merit in the analysis of resected cases. The UICC staging system may be more suitable for analyses of both resected and non-resected patients. It is recommended that patient data should be recorded according to both JPS and UICC staging systems with both clinical and pathological information.