Published online Jan 26, 2019. doi: 10.12998/wjcc.v7.i2.145
Peer-review started: August 14, 2018
First decision: October 5, 2018
Revised: November 13, 2018
Accepted: November 23, 2018
Article in press: November 24, 2018
Published online: January 26, 2019
Gastric cancer (GC) is a common type of cancer with a high incidence of cancer-related death. Early gastric cancer (EGC), which comprises of T1 tumors irrespective of lymph node metastasis, is a special type of cancer. Although GC is often diagnosed at an advanced stage, the incidence of EGC is increasing. Recently, the eighth edition of the American Joint Committee on Cancer (AJCC) tumor lymph node metastasis (TNM) staging system for stomach carcinoma was published. This edition retains the same T, N, and M classifications as the seventh edition. However, several studies found that the AJCC TNM staging system was inadequate for EGC.
An accurate staging system for malignancy is useful to make the postoperative treatment decisions and follow-up plans. Although the AJCC system is a worldwide used staging system, the N staging system is still occasionally questionable. The eighth edition of the TNM staging system stratifies GC without distal metastasis into seven risk groups according to the pathological T and N categories. However, the classification scheme of the AJCC staging system is primarily based on the advanced GC. In EGC, lymph node metastasis is less severe than that in advanced GC. Whether the AJCC TNM staging system is also appropriate for T1 cancer remains to be decided, but few studies have focused on this topic.
The aim of this study was to identify a better TNM classification to improve the prognostic prediction of patients with EGC after curative surgery.
We re-evaluated the long-term survival of patients with EGC who underwent radical gastrectomy from the SEER database between 1988 and 2011 in the context of the eighth edition of the AJCC staging system, and identify a better TNM classification to improve the prognostic prediction of patients with EGC after curative surgery. We also compared the discriminatory value of the new TNM classification with that of the eighth edition of the AJCC TNM staging system. Additional external validation was performed using the dataset from Fujian Medical University Union Hospital, China with similar inclusion and exclusion criteria. Overall survival was analyzed using the Kaplan-Meier method, and log-rank tests were used for statistical comparisons of the survival curves. X-tile program (http://www.tissuearray.org/rimmlab/) was used to produce the LN cutoff points with the minimum P-values from log-rank χ2 statistics for the categorical metastatic LNs in terms of survival. The Akaike Information Criterion and the Harrell’s concordance index (c-statistic) were used to assess the relative discriminatory abilities of different TNM staging systems.
The OS between N1 and N2, or between N3a and N3b cancers did not differ significantly in cases of EGC. We identified a new metastatic lymph node classification for EGC consisting of T1N0, T1N1’ (1-6 metastatic LNs), and T1N2’ ( ≥ 7 metastatic LNs) using X tile program. The OS of patients in T1N1’ stage was similar to the 8th edition AJCC stage IIA disease, while the OS of patients in T1N2’ stage was not significantly different from that of stage IIB disease. The new TNM staging system exhibited a slightly better predictive ability of OS for EGC in the training set and an external validation set.
The LN metastasis classification of the eighth edition of the AJCC TNM staging system has variation in survival for AGC patients but is still associated with some stage migration in EGC. We have developed an optional new TNM staging system that can be used to accurately predict the 5-year OS of patients with EGC. However, more prospective studies with different populations are needed in the future.
EGC is a special type of tumor that comprises of T1 (invading the mucosa or submucosa) tumors irrespective of lymph node metastasis. The 5-year survival rate of patients with EGC usually exceeds 90% in some Asian and Western countries. However, nearly 10% of patients still experience recurrence or death. An accurate staging system for malignancy is useful for making the postoperative treatment decisions and follow-up plans. We have developed an optional new TNM staging system with a better predictive ability of overall survival for EGC. This topic requires further analysis in a larger patient subset and in randomized studies in the future.