Is the 8th Edition of the AJCC TNM Staging System Sufficiently Reasonable for All Patients with Noncardia Gastric Cancer? A 12,549-Patient International Database Study.

BACKGROUND: The aim of this work is to compare the prognostic ability between the 7th and 8th editions of the American Joint Committee on Cancer (AJCC) tumor-node-metastasis (TNM) classification for gastric cancer (GC).

METHODS: A total of 10,194 noncardia GC patients were identified from the Surveillance, Epidemiology, and End Results database from 1988 to 2008. Concordance index (C-index), bayesian information criterion (BIC), and time-dependent receiver operating characteristic (t-ROC) analyses were used. External validation was performed using a dataset (n = 2355) derived from Fujian Medical University Union Hospital.

RESULTS: Overall survival for all five AJCC N categories differed significantly when patients were subgrouped into ≤ 15 versus >15 examined lymph nodes (eLNs). The prognostic ability of the 8th edition (C-index 0.716) was not improved over the 7th edition (C-index 0.716). Subgroup analysis showed superior performance of the 8th over the 7th edition in patients with > 15 eLNs (C-index 0.742 vs. 0.735); however, the two editions showed similar performance for patients with ≤ 15 eLNs (C-index 0.713 vs. 0.713). The BIC and t-ROC analyses were consistent. To better predict the prognosis of patients with ≤ 15 eLNs, we established a novel prognostic model based on independent prognostic factors (C-index 0.735). BIC analysis showed that this new model was better than the 7th and 8th editions. Similar results were obtained from the validation set.

CONCLUSIONS: The 8th edition of the AJCC TNM classification shows better prognostic ability than the 7th edition in noncardia GC patients with > 15 eLNs, but no improvement was found in patients with ≤ 15 eLNs; therefore, a novel prognostic model is proposed.