Aims: Neoadjuvant chemotherapy followed by surgery is the standard of care for patients with gastro-oesophageal adenocarcinoma. The aims were to validate the utility of the tumour regression grade (TRG) in patients who have received chemotherapy and to investigate if (i) TRG correlates with tumour downstaging and (ii) TRG could provide a comparative platform for future predictive biomarker investigations.
Methods and results: Three pathologists were blinded to the treatment approaches. Review included diagnosis, tumour grade, TNM staging, vascular invasion, perineural invasion, resection margin involvement and histopathological response to chemotherapy, as measured by TRG. In the neoadjuvant chemotherapy (CS) group (n = 84), 46.7% of gastric/gastro-oesophageal junction adenocarcinomas, and 45.5% of lower third oesophageal adenocarcinomas had TRG 1, 2 or 3 compared with 13.7% in the primary surgery group (n = 124) (P < 0.001 and P = 0.006, respectively). In the CS group, responders (TRG 1, 2 or 3) showed significant tumour downstaging [early ypT-stage disease (P = 0.002)]. In gastric cancers specifically, additional associations were seen with negative nodal disease (P = 0.044) and absence of vascular invasion (P = 0.027).
Conclusions: TRG may reflect response to chemotherapy. In addition, positive correlations between TRG and ypTNM staging were demonstrated that would suggest tumour downstaging.