Tumor-Associated Macrophages and Regulatory T Cells Infiltration and the Clinical Outcome in Colorectal Cancer

The aim of the study is the assessment of the intensity of the infiltration of tumor-associated macrophages (TAMs) CD68(+)/iNOS(-) and Tregs CD8(+)/FoxP3(+) in colorectal cancer (CRC) patients as prognostic factors with respect to disease-free survival (DFS) and overall survival (OS). In this retrospective study, tissue samples were obtained from 89 patients undergoing resection for CRC (stage IIA, pT3N0M0 and stages IIIB and IIIC, pT3N1-2M0). Recurrence was observed in 45 patients at the time of the follow-up (10 local recurrences, 35 distant metastases). In patients with recurrence the following were present: a tendency to an older average age at the time of diagnosis (p = 0.07), higher nodal involvement (p = 0.002) and more advanced clinical disease (p = 0.01). The analysis of the clinical data and immunohistochemical studies were performed with the methodology of identification of TAM and Treg subsets in histological sections, with the aim to use it in routine clinical management. Both DSF and OS were the clinical parameters assessed in the study. The presence of intense infiltration of TAMs in the tumor stroma was related to shorter DFS (p = 0.005) and OS (p = 0.006). The opposite tendency was observed in the tumor front (p = 0.061). The relative risks of recurrence and cancer-related death were more than twice higher in the group of patients with intense infiltration of TAMs in the tumor stroma (RR 2.05, 95% CI 1.33-3.14; p = 0.001 and RR 2.08, 95% CI 1.28-3.39; p = 0.003, respectively). Intense infiltration of Tregs in the tumor stroma was related to shorter DFS and OS (p < 0.0001). The relative risks of recurrence and death in a group of patients with intense infiltration of Tregs in the tumor stroma were more than 12 times higher than in patients with less intense infiltration (RR 12.3, 95% CI 5.44-27.9; p < 0.0001 and RR 12.5, 95% CI 4.9-32.4; p < 0.0001, respectively). Infiltration of TAMs CD68(+)/iNOS(-) and Tregs CD8(+)/FoxP3(+) in the tumor stroma are negative prognostic factors with a positive correlation between them. Tregs may constitute an independent prognostic factor in patients with CRC.