Comparison of the eighth and seventh editions of the American Joint Committee on Cancer TNM staging systems for gastric cancer: proposal for a simplified and improved TNM staging system

Background

To evaluate the prognostic significance of the eighth edition of American Joint Committee on Cancer (AJCC) TNM staging classification for gastric cancer.

Methods

Data from 4,957 consecutive patients who underwent radical gastrectomy between 1997 and 2014 were retrieved from our database. The prognostic value of the eighth edition was compared with that of the seventh edition of the AJCC TNM classification. The analysis was repeated in an external validation set.

Results

Significant differences in 5-year overall survival (OS) rates were observed for each TNM stage when using the eighth edition system, and smaller AIC values and a higher c-statistic were observed relative to those of the seventh edition. However, the OS rates in each subgroup of stage III patients in the eighth edition were significantly different. Additionally, patients with the same pN stage, namely the pT4a and pT4b groups, showed similar 5-year OS. Based on the survival data, we propose a simplified staging system. In the improved TNM (iTNM) staging system, the subgroups of a given TNM stage do not have statistically significant OS differences. The iTNM staging exhibits superior prognostic stratification, with lower AIC values and a higher c-statistic than the eighth edition TNM classification. Similar results were obtained with the external validation dataset.

Conclusions

The eighth edition of the AJCC TNM classification provides superior prognosis to that of the seventh edition. However, it remains associated with some stage migration. The iTNM staging system permits simplification and slightly better prognostic prediction.

Clinical trial identification

Legal entity responsible for the study

Changming Huang

Funding

None

Disclosure

All authors have declared no conflicts of interest.