ypT0 gastric carcinoma after preoperative chemotherapy: a unique status according to AJCC 8(th) edition cancer staging system

BACKGROUND: American Joint Committee on Cancer (AJCC) recently had published 8th edition staging system, in which a separate staging system was proposed for gastric cancers those received preoperative therapy (ypStage), however ypT0 was not included. The aim of this study was to propose the inclusion of ypT0 into the new staging classification. METHODS: We collected data of gastric cancer patients who underwent gastrectomy after preoperative chemotherapy in the First Affiliated Hospital of Zhejiang University (2004–2015). Kaplan-Meier survival estimations and log-rank tests were performed to compare survival. RESULTS: 314 patients were enrolled in this study according to inclusion and exclusion criteria. The 5-year overall survival (OS) rate of all patients was 53.5% and the survival estimation was well discriminated by ypstage (P<0.001). Twenty-five patients were identified achieving pathological complete regression in primary lesion (ypT0), in which there were 16 pCR patients and 9 ypT0N+ patients. The 5-year OS of pCR patients was 93.8%, which was not better than ypstage I with 5-year OS of 97.5% (P=0.507). Meanwhile, ypT0N+ patients’ 5-year OS was 66.7%, which was significantly shorter than those with ypstage I (P=0.002), but no statistical difference from ypstage II with 5-year OS of 71.6% (P=0.583). CONCLUSIONS: Complete pathological regression of primary lesion (ypT0) was a predictor for long-term outcomes. pCR and ypT0N+ patients might be considered for inclusion in the ypstage I and ypstage II group respectively.