Comparison between 7th and 8th edition of AJCC TNM staging system for gastric cancer: old problems and new perspectives

Gastric cancer (GC) represents one of the most common causes of cancer mortality worldwide (1). Although considerable progress in diagnostic and therapeutic tools can improve the outcome of GC patients, surgery remains the only curative therapy. Actually, surgical resection with lymphadenectomy is considered the only curative therapeutic approach for resectable GC, while preoperative and adjuvant chemotherapies, as well as chemoradiation, can improve the outcomes aiming at the reduction of recurrence and extension of survival. However, lymphadenectomy for surgical treatment of GC has remained an open issue between the European and Japanese surgical schools for several years. At present, on the basis of scientific and practical outcomes, the Western perspective regarding the lymphadenectomy in GC surgery has been overturned. As a result, the majority of national as well as several supranational scientific societies are converging on the D2 lymphadenectomy as the standard of care with curative intent (2). The main goal of GC surgery is to preserve the post-operative functionality as well as the quality of life and maximize long-term oncological outcomes by means of proper surgical approach with a tailored lymphadenectomy (3,4). To this address, precise classification of the tumor stage, incorporating the lesion depth (T parameter), lymph node involvement (N parameter) and the presence of distant metastases (M parameter), is of paramount importance for prognostic assessment and stage-specific therapeutic strategy (5). The American Joint Committee on Cancer (AJCC)/Union for International Cancer Control (UICC) tumor, node, metastasis (TNM) staging system has been extensively used for clinical research and practice in defining GC stage, representing the most relevant tumor-related prognostic factor (6). Over the past 30 years there is been a succession of several versions of this classification system and, since 2017, the 8th edition of TNM staging system has been introduced, resulting in several changes from the previous version (7). First of all, the anatomic landmark between the esophagus and the stomach has been redesigned: esophagogastric junction (EGJ) cancers with the center of lesion confined to the first two centimeters of the proximal stomach are defined as esophageal cancers. EGJ cancers extending over two centimeters of the upper stomach are defined as gastric neoplasms. Additionally, although the division of pN3 in pN3a (7–15 positive lymph nodes) and pN3b (more than 15 positive lymph nodes) was already introduced in the 7th edition, no change in