Assessment of Histopathological Response in Gastric and Gastro-Oesophageal Junction Adenocarcinoma following Neoadjuvant Chemotherapy: Which Scoring System to Use?

Background. The standard of care for patients with operable gastric and gastro-oesophageal junction (GOJ) tumours involves neoadjuvant chemotherapy. This improves survival and reduces risk of tumour recurrence following surgery. The various grading criteria published to assess histological response to neoadjuvant treatments have never been compared in terms of their reproducibility and ability to predict survival. Methods. A study was carried out of 66 patients with gastric and GOJ (types II and III) adenocarcinoma treated with neoadjuvant chemotherapy according to the MAGIC protocol. Histology slides were reviewed independently by two histopathologists using three published grading systems (Mandard, Japanese, and Becker). Histological, demographic, and survival data were collected. The kappa statistic was used to assess interobserver reproducibility. Results. Three (5%) patients had a complete pathological response. There was reasonable interobserver agreement for the grading systems: κ-scores = 0.44 (Mandard), 0.28 (Japanese), and 0.51 (Becker). Only Mandard and Becker scores provided prognostic information: 5-year overall survival rates of 100% for complete or near complete responders versus 35% for nonresponders (<0.05) for both. Positive lymph nodes (=0.004) and resection margins (=0.004) were associated with poor survival. Conclusion. Becker’s score is most reproducible for the evaluation of histological response. Furthermore, lymph node and resection margins status provides prognostic information.