ESMO Asia Virtual Congress 2020

Abstract 136P

Background

The benefits of neoadjuvant therapy for patients with locally advanced gastric cancer (GC) are increasingly recognized. The 8th edition of the AJCC Staging Manual first proposed ypTNM staging, but its accuracy is controversial. This study aims to develop a modified ypTNM staging.

Methods

Clinicopathological data of 1791 patients who underwent curative-intent gastrectomy after neoadjuvant therapy in the SEER database, as the development cohort, were retrospectively analyzed. Modified ypTNM staging was established based on overall survival (OS). We compared the prognostic performance of the AJCC 8th ypTNM staging and the modified staging for patients after neoadjuvant therapy.

Results

In the development cohort, the 5-year OS for AJCC stage I, II, and III was 58.8%, 39.1%, and 21.6%, respectively, compared with 69.9%, 54.4%, 34.4%, 24.1%, and 13.6% for modified ypTNM stage IA, IB, II, IIIA, and IIIB. The modified staging had better discriminatory ability (C-index: 0.620 vs. 0.589, p < 0.001), predictive homogeneity (likelihood ratio chi-square: 140.71 vs. 218.66, p < 0.001), predictive accuracy (mean difference in BIC: 64.94; NRI: 35.54%; IDI: 0.032, all p<0.001), and model stability (time-dependent ROC curves) over AJCC. Decision curve analysis showed that the modified staging achieved a better net benefit than AJCC. In external validation (n = 266), the modified ypTNM staging had superior prognostic predictive power (all p<0.05).

Conclusions

We have developed and validated a modified ypTNM staging through multicenter data that is superior to the AJCC 8th ypTNM staging, allowing more accurate assessment of the prognosis of GC patients after neoadjuvant therapy.