Comparison between AJCC 8th edition gastric and esophageal ypTNM classification system in Siewert II esophagogastric junction adenocarcinomas: A retrospective study based on Eastern and Western Data.

[INTRODUCTION] Multimodal therapy has become the standard treatment for curable upper gastrointestinal cancers. However, it remains unclear which 8th edition AJCC post-neoadjuvant therapy pathological classification system, esophageal (ypTNM-EC) or gastric (ypTNM-GC), can predict the overall survival (OS) of patients with Siewert II adenocarcinomas better.

[METHODS] Patients diagnosed with Siewert II adenocarcinomas receiving neoadjuvant therapy plus curative resection at the University Medical Center Utrecht (UMC Utrecht) and the Peking University Cancer Hospital (PUCH) between the 2001 and 2022 were included in this study. The patients from two institutions were analyzed separately. Predictive univariable and multivariable Cox models based on ypTNM-EC and ypTNM-GC were constructed. The C-index and calibration curves were used to compare the predictive abilities of ypTNM-EC and ypTNM-GC Cox models.

[RESULTS] A total of 125 patients from UMCU and 145 from PUCH were included. There was no significant difference in the C-index between the ypTNM-EC and the ypTNM-GC univariable and multivariable Cox models in the UMC Utrecht (p-value = 0.883; p-value=0.681) and PUCH (p-value = 0.808; p-value=0.548) cohorts, and no significant difference was observed between their calibration curves in the two cohorts.

[CONCLUSION] The AJCC 8th edition ypTNM prognostic classification systems for esophageal and gastric cancer demonstrated no difference in predicting OS for patients with Siewert II adenocarcinomas both in the Western and Eastern data. The ypTNM-GC, with fewer stage groups, may offer greater convenience for clinical application.