Immunoscore is a strong predictor of survival in the prognosis of stage II/III gastric cancer patients following 5-FU-based adjuvant chemotherapy.

The prognostic impact of Immunoscore (IS) in gastric cancer (GC) patients treated with adjuvant chemotherapy remains unelucidated. We evaluated the CD3 + , CD8 + , and Foxp3 + T-lymphocyte densities in tumor centers and invasive margin regions of 389 patients with surgically resected stage II/III GC who received 5-FU-based adjuvant chemotherapy and investigated the impact of IS on survival. In univariate analysis, high CD3 + , CD8 + , and Foxp3 + T-lymphocyte densities in the invasive margin were correlated with better prognosis (all P < 0.05). Patients with high IS had significantly longer disease-free survival (DFS; P < 0.001) and overall survival (OS; P < 0.001). In multivariate analysis, IS demonstrated a powerful prognostic impact on patient outcome [DFS, hazard ratio (HR) = 0.465; 95% confidence interval (CI), 0.306-0.707, P < 0.001; OS, HR = 0.478; 95% CI, 0.308-0.743, P = 0.001]. Additionally, although all EBV-positive cases had high IS, IS was similar in both microsatellite instability (MSI)-high and microsatellite stable (MSS)/MSI-low groups (83.3% and 80.5%, respectively). Subgroup analysis according to MSI status revealed that high IS patients had significant DFS and OS benefits in both MSS/MSI-low (DFS, HR = 0.527, 95% CI, 0.341-0.816, P = 0.004; OS, HR = 0.528, 95% CI, 0.334-0.837, P = 0.007) and MSI-high (DFS, HR = 0.166, 95% CI, 0.033-0.826, P = 0.028; OS, HR = 0.177, 95% CI, 0.036-0.883, P = 0.035) groups. Thus, the assessment of immune cell infiltration based on IS may provide a strong indicator of survival in stage II/III GC patients with curative resection following 5-FU-based adjuvant chemotherapy.