P-111 - A simplified and efficient modified TNM staging system for patients with gastric cancer after radical gastrectomy

Abstract

Introduction: The seventh edition of the American Joint Committee on Cancer (AJCC) staging classification for stomach carcinoma has been used worldwide. However, there were still some controversies regarding this staging system. We investigated the validity of the 7th edition of the American Joint Committee on Cancer (AJCC) classification system and developed a modified TNM (mTNM) staging system for improving the prognostic prediction of patients with gastric cancer after curative surgery. Methods: Data from 4957 consecutive patients who underwent radical gastrectomy between 1997 and 2014 were retrieved from our database. Kaplan-Meier analyses were performed for each subject’s TNM stages in a comparative manner. The relative discriminatory abilities of different staging systems were assessed using the Akaike’s Information Criterion (AIC) and Harrell’s concordance index (c-statistic). Additional external validation was performed using a dataset (n = 3803) from the National Cancer Institute’s Surveillance, Epidemiology, and End Result (SEER) database. Results: The 5-year overall survival (OS) of the entire cohort was 58.0%. according to the 7th of the AJCC guidelines, the OS rate in each subgroup of stage IIIB and stage IIIC patients was significantly different, and for patients with the same pN stages, the pT4a and pT4b groups had a similar 5-year OS (P > 0.05). Basis on the survival data, we revised the stage grouping system. In the mTNM staging system, the overall survival rates were without statistics different for each subgroup in the same TNM stage. The mTNM staging exhibited superior prognostic stratification with lower AIC values and a higher c-statistic compared to the seventh edition TNM classification. Similar results were found in the external validation dataset from the SEER database. Conclusion: The seventh edition AJCC TNM classification is associated with some stage migration. Our modified TNM staging system seems to be simplified yet showed better predictability of overall survival for patients with gastric cancer after radical gastrectomy.