Comparison of two major staging systems of esophageal cancer—toward more practical common scale for tumor staging
The latest 8th edition of TNM Classification of Malignant Tumours by Union for International Cancer Control (UICC) and 11th edition of Japanese Classification of Esophageal Cancer by Japan Esophageal Society (JES) are the two major classifications widely accepted as tools for clinical staging of esophageal cancer. Both systems consist of three main categories, i.e., T, N, and M, but large difference exists between the two. JES system has more detailed sub-classification of T1 tumors reflecting meticulous work by Japanese investigators on superficial esophageal cancer. N-category shows the largest difference. UICC defines the N-category according to only the number of the metastatic regional lymph nodes. The definition of regional nodes in UICC system is static and uniform, and supraclavicular nodes are definitely excluded. In JES system, regional nodes are subgrouped into five different patterns according to the main tumor location, and the supraclavicular nodes are always regional nodes for thoracic esophageal cancer. Japanese surgeons have described the evidence that regional nodes should be dynamically defined according to tumor location and supraclavicular nodes should be included in regional nodes. Compared to the simplified N-category, the staging matrix of UICC system is somewhat complicated. The clinical stage and pathological stage of UICC system are not identical and difference exists also between squamous cell carcinoma (SCC) and adenocarcinoma. It has another system of pathological prognostic grouping. We can imagine several reasons for the difference occurred between the two systems. One is the difference of major pathology. Another reason is the difference of basic concept of cancer treatment. The relative “dependence” on radical surgery in Japan has required the detailed definition of each lymph node station and the evaluation of “efficacy index” of each station. The strict and detailed definition of lymph node stations has been regarded as an obstacle to those who are not familiar with it. Some simplification can be done but maintaining dynamic definition of regional lymph nodes linked to tumor location. If UICC system can accept this concept, I think the two systems can be unified to realize more practical and useful staging system as an international common language.