Immune Cell Infiltrate and Prognosis in Gastric Cancer

SIMPLE SUMMARY: Differences in the composition of immune cell infiltrate between individual tumors have been shown to have prognostic significance in several cancer types. In gastric cancer, both assessing immune cell infiltrate from routinely hematoxylin–eosin-stained slides and immunohistochemically stained slides seems promising. In this study, we assessed immune cell infiltrates by their hematoxylin–eosin-based Klintrup–Mäkinen (KM) grades in a large cohort of 741 gastric cancer patients and compared them with immunohistochemistry-based immune cell scores. The KM grades had more prognostic value in the study cohort than the immune cell scores. Based on our results, the KM grade has good prognostic value in gastric cancer. Immunohistochemical stainings of lymphocytes might not provide additional prognostic information over routinely stained hematoxylin–eosin slides. ABSTRACT: Purpose: To examine and compare the prognostic value of immune cell score (ICS) and Klintrup–Mäkinen (KM) grade in gastric cancer. Methods: Gastric adenocarcinoma tissues from samples of 741 patients surgically treated in two hospitals in Finland were assessed for ICS and KM grade. Cox regression with adjustment for confounders provided hazard ratios (HRs) and 95% CIs. Subgroup analyses were performed in intestinal and diffuse type subgroups. The primary outcome was 5-year overall survival. Results: High ICS was associated to longer 5-year survival (adjusted HR 0.70, 95% CI 0.52–0.94), compared to low ICS. The difference was significant in intestinal type subgroup (adjusted HR 0.54, 95% CI 0.36–0.81) but not in diffuse type subgroup (adjusted HR 0.92, 95% CI 0.58–1.46). High KM grade was an independent prognostic factor for longer 5-year overall survival (adjusted HR 0.59, 95% CI 0.45–0.77) in both intestinal (adjusted HR 0.61, 95% CI 0.44–0.85) and diffuse subgroups (adjusted HR 0.52, 95% CI 0.31–0.86). ICS and KM grade were moderately correlated (ρ = 0.425). When both immune cell score and KM grade were included in the regression analysis, only KM grade remained prognostic. Conclusions: Both ICS and KM grade are prognostic factors in gastric adenocarcinoma, but immunohistochemistry-based ICS might not have additional prognostic value over hematoxylin–eosin-based KM grade.