Staging gastric cancer patients after complete surgical resection: which system should we use?

The most commonly used staging system for gastric adenocarcinoma is the American Joint Committee on Cancer (AJCC) tumor, node, metastasis (TNM) staging system. The 2010 7th edition of the AJCC system made several changes from the 6th edition, including redefining T and N categories and moving the staging of proximal gastric tumors within 5 cm of the gastroesophageal junction to the esophageal cancer staging system. TNM stage grouping were also redefined, with stage II further divided into IIA and IIB and stage IIIA and IIIB further divided into IIIA, IIIB, and IIIC. Since the publication of the 7th edition AJCC staging system in 2010, several single and multi-institution studies have compared the 6th and 7th editions. Some studies have found the 7th edition to be superior. Other studies have found the 7th edition to be either inferior to or no better than the 6th edition. Two studies from the same institution found opposing results. All these studies vary in the sort of patients examined, the extent of surgery and pathological analysis, and the methods of data analysis. In this issue of Annals of Surgical Oncology, Dikken et al. compare disease-specific survival predictions for patients with gastric adenocarcinoma using the 6th and 7th editions of the AJCC staging system. Patients underwent surgery either at Memorial Sloan-Kettering Cancer Center (MSKCC) in New York or at one of several institutions in the Netherlands as part of the Dutch Gastric Cancer Trial (DGCT). In this group of 2,196 patients, the authors find that the predictive accuracy of the 7th edition N categories is improved based on concordance measurements, but the predictive accuracy of the 7th edition TNM stages is decreased. Survivals using the AJCC 6th edition did not significantly differ for two of the six stage groups, while survivals using the 7th edition did not significantly differ for three of the seven stage groups. Thus, the authors conclude the AJCC 7th edition staging system has increased complexity with no improvement in predictive accuracy. Dikken et al. put together a large cohort of Western patients treated with relatively extensive lymphadenectomies and perform a thorough comparison of the 6th and 7th AJCC staging systems. One primary advantage of this study is the use of data from several institutions in two different countries. Most previous studies on this topic are from Asian countries, so this multi-institution study of Western patients is important in determining whether we are making progress with the AJCC staging system revisions. However, as with most studies of this nature, there are several potential problems. First, the extent of lymphadenectomy for this cohort of patients varied, which causes problems with stage migration. At MSKCC, ‘‘most patients underwent a D2 lymph node dissection’’ and DGCT patients were randomized to D1 versus D2 node dissection. Furthermore, 22–28 % of patients in this study had \15 nodes examined, and the AJCC staging system suggests ‘‘that at least 16 regional nodes be assessed pathologically.’’ Second, the varying extent of lymphadenectomy and adjuvant therapies for patients in this study may have affected pathological staging and survival. Sixteen percent of MSKCC patients received neoadjuvant chemotherapy, which can result in downstaging the T and/or N stages. The 15-years follow-up from the Dutch trial now demonstrates a significant 12 % Society of Surgical Oncology 2012