A comparative study of the application of AJCC 6th and 7th edition gastric cancer staging systems in remnant gastric cancer and the establishment of a prognosis prediction model

Abstract Background Remnant gastric cancer (RGC) is a serious complication after gastrectomy that affects the long-term survival rate. At present, there is no international staging system specifically designed for RGC, and clinicians often use the TNM gastric cancer staging system to stage patients with RGC. Therefore, the purpose of this study was to compare the applicability of American Joint Committee on Cancer (AJCC) version 6 and version 7 in patients with RGC, and to try to establish a new prognostic prediction model to help clinicians more accurately and reliably assess the severity of patients' disease. Method This study reviewed 110 patients with RGC at West China Hospital from January 1998 to December 2018. The applicability of the two staging systems in patients with gastric stump cancer was analyzed by comparing the C-index applied to the two staging systems in patients with gastric stump cancer. Through univariate and multivariate COX regression analysis of survival data of patients with stump gastric cancer, independent risk factors affecting prognosis of patients with stump gastric cancer were identified. The independent risk factors were analyzed and a new staging system was established. Results Among the patients with no change in staging between the two versions, there were 67 cases, and the rate of staging deviation was 39%. The C-index for T staging of AJCC6 and 7 versions was 0.70 (P=0.12), the C-index for N staging of AJCC6 version was 0.635, and the C-index for N staging of AJCC7 version was 0.645 (P=0.23). The C-index for TNM staging of AJCC6 version was 0.76, and the C-index for TNM staging of AJCC7 version was 0.732 (P=0.09). A nomogram was created using the independent risk factors, and internal validation was performed using the bootstrap method, which showed good prognostic prediction. Conclusion: AJCC6 staging system demonstrated a trend of superiority in applicability compared to AJCC7 staging system. A new prognostic model was established for RGC patients.