Neoadjuvant Gastric Score: How Response to Neoadjuvant Chemotherapy Affects Overall Survival and Adjuvant Benefit.

INTRODUCTION:The Neoadjuvant Rectal score (NAR) was developed as a short-term surrogate for 5-year overall survival (OS) prediction in locally advanced rectal cancer on the basis of response to neoadjuvant therapy. We aim to assess whether this score can be repurposed for locally advanced gastric adenocarcinoma treated with neoadjuvant chemotherapy followed by surgical resection. METHODS:Patients with gastric adenocarcinoma treated with neoadjuvant systemic therapy followed by surgical resection were extracted from the National Cancer Database. Neoadjuvant Gastric (NAG) scores were calculated, and patients were stratified into low-, intermediate-, and high-score categories, with low scores predicting longer survival. Patients were propensity-matched 1:1:1 between the groups for OS comparison. We also matched patients within each group 1:1 per receipt of adjuvant therapy and compared 5-year OS. RESULTS:There were 2,970 patients identified. NAG classified patients into low- (n = 396, 13.3%), intermediate-(n = 756, 25.5%), and high (n = 1818, 61.2%) groups. After propensity matching, 5-year OS was significantly different between the matched groups (low-NAG 82%, intermediate-NAG 73%, and high-NAG 39%; p < 0.001). NAG score grouping also predicted OS benefit of adjuvant therapy; low- and intermediate-NAG patients had no OS benefit with adjuvant therapy (86% vs. 84%; p = 0.492, and 77% vs. 74%; p = 0.382, respectively), whereas patients with high-NAG score had a 5-year OS benefit with adjuvant therapy (39% vs. 29%; p = 0.024). CONCLUSION:NAR score may be repurposed to generate a prognostic tool in gastric adenocarcinoma to predict 5-year OS and has the potential to guide decision-making regarding allocation of adjuvant therapy. Further studies should prospectively validate these findings to confirm clinical utility.