Tumor-infiltrating CD8+ T cells combined with tumor-associated CD68+ macrophages predict postoperative prognosis and adjuvant chemotherapy benefit in resected gastric cancer

BACKGROUND: Tumor-infiltrating immune cells are present in various malignant tumors, but their clinical significance in gastric cancer (GC) remains unclear. This study aimed to investigate the prognostic significance of tumor-infiltrating lymphocytes (TILs) and tumor-associated macrophages (TAMs). METHODS: Using a prospective database containing 401 cases of GC, we evaluated TIL (cluster of differentiation 8 (CD8) expression) and TAM (cluster of differentiation 68 (CD68) expression) statuses via immunohistochemical staining. RESULTS: Compared with CD8+ TIL-negative cases (n = 196, 48.6%), CD8+ TIL-positive cases (n = 205, 51.1%) showed significantly better recurrence-free survival (RFS) [log-rank p<0.001; multivariate HR: 0.372; 95% confidence interval (CI): 0.239–0.579, p<0.001]. In contrast, compared with CD68+ TAM-negative cases (n = 217, 54.1%), CD68+ TAM-positive cases (n = 184, 45.9%) had significantly poor RFS [log-rank p<0.001; multivariate HR: 2.182; 95% CI: 1.435–3.318, p<0.001]. Thus, patients with a positive CD8+ TIL and negative CD68+ TAM status exhibited significantly increased RFS. Multivariate analysis demonstrated that CD8+ TILs and CD68+ TAMs may serve as independent prognostic markers for RFS. Incorporating CD8+ TIL and CD68+ TAM statuses into the AJCC TNM system generated a predictive model with better predictive accuracy for RFS. More importantly, patients with a positive TIL and negative TAM status showed a tendency of improved RFS after postoperative adjuvant chemotherapy (PAC). Similar results were obtained by overall survival (OS) analysis. CONCLUSIONS: CD8+ TIL and CD68+ TAM statuses were identified as independent prognostic factors that may be integrated into the current TNM staging system to refine risk stratification and to better predict the survival benefit from PAC in patients with GC. TRIAL REGISTRATION: The current controlled trial was registered at ClinicalTrials.gov (ID: NCT02327481) on December 30, 2014. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12885-019-6089-z) contains supplementary material, which is available to authorized users.