Background and objectives: T regulatory lymphocytes (Treg) are one of the subsets of T-lymphocytes involved in the interaction of neoplastic tumors and the host immune system, and they may impair the immune reaction against cancer. It has been shown that Treg are increased in the peripheral blood of patients with various cancers. In colorectal cancer, the prognostic role of Treg remains controversial. Colorectal cancer is a heterogenous disease, with many variations stemming from its primary tumor location. The aim of this study is to analyse the relationship between the amount of Treg in the peripheral blood of patients with left-sided colorectal cancer in various stages of disease and long-term survival. Materials and Methods: A prospective analysis of 94 patients with left-sided colorectal cancer and a group of 21 healthy volunteers was carried out. Treg levels in peripheral blood were analysed using flow cytometry. Results: There was a statistically significant difference between the amount of Treg in the Ist and IInd TNM stages (p = 0.047). The number of Treg in the entire study group was significantly lower than in the control group (p = 0.008) and between patients in stages II and III and the control group (p = 0.003 and p = 0.018). The group of pT3+pT4 patients also had significantly lower Treg counts in their peripheral blood than the control group (p = 0.005). In the entire study group, the level of Treg cells in the peripheral blood had no influence on survival. The analysis of the TNM stage subgroups also showed no difference in survival between patients with "low" and "high" Treg counts. Conclusion: The absolute number of Treg in the peripheral blood of patients with left-sided colorectal cancer was significantly decreased in comparison to healthy controls, especially for patients with stage II+III disease. Treg presence in the peripheral blood had no impact on survival.
Keywords: CD4+CD25+Fox3+ cells; T-regulatory cells (Treg); left-sided colon cancer; overall survival; peripheral blood; prognosis; prognostic biomarker.