Revised points and disputed matters in the eighth edition of the TNM staging system for gastric cancer

The American Joint Committee on Cancer and the Union for International Cancer Control have now released the eighth edition of the cancer staging system, which incorporates some major revisions concerning gastric cancer. First, grouping of pathological stages has been revised in accordance with a proposal from the International Gastric Cancer Association. That revision was based on analysis of survival of more than 25 000 patients worldwide who had undergone curative gastrectomy without neoadjuvant therapy. Stratification of survival in Stage III subgroups has been improved by subdividing N3 into N3a and N3b. Second, a simplified grouping of clinical stages that differs completely from grouping of pathological stages has been proposed. Pre-treatment depth of tumour invasion is now categorized as T1/T2, T3/T4a or T4b, and lymph node status is simply categorized as N0 or N+. Additionally, a 'yp-stage' for specimens resected after neoadjuvant therapy has been newly proposed. These clinical and post-neoadjuvant stages were considered useful now that neoadjuvant chemotherapy is increasingly being administered to patients with potentially resectable gastric cancer. Third, staging of oesophagogastric junction tumours has been modified; Siewert type 3 tumours are now classified as gastric tumours and are staged according to the gastric, rather than the oesophageal, system. More appropriate staging of gastric cancers treated with neoadjuvant therapy, and/or new staging systems incorporating variables other than T/N/M, such as biological or genomic markers, are likely future developments.