e15510 Background: Tumor is a structure where malignant cells interact, among others, with cells of the adaptive and innate immune systems largely determining the tumor microenvironment. The role of TILs in the disease prognosis has been shown. The amount of CTCs is one of the factors that significantly affect the risk and rate of metastasis. The purpose of the study was to assess an association between TILs and CTCs in the peripheral blood of patients with various stages of colorectal cancer (CRC). Methods: The study included 299 patients (aged 42-86 years, mean age 64.2±1.7) with stage II-IV CRC T1-4N0-2M0-1. TILs were identified in tumor material after standard histological processing. Lymphocytes were counted per 100 epithelial cells in 5 fields of view at a magnification of x400; the result was expressed as a percentage ( < 5% weak, 5-30% moderate, >30% strong). The numbers of CTCs were measured in the peripheral blood using the Veridex CellSearch system (Janssen), taking into account the expression of epithelial cell adhesion markers EpCAM, cytokeratins 8,18,19 and absence of the CD45 expression. The blood sample was evaluated according to the following criteria: 0 CTCs, 1-3 CTCs, and more than 3 CTCs. Statistical analysis of results was performed in the Statistica 13.0 program (StatSoftInc., USA). Results: Weak lymphocytic infiltration was detected in 32.8%, moderate - in 48.1%, strong - in 19.1% of cases. CTCs were detected in 62.9% cases (in 188 of 299 patients). The percentages of patients with 1-3 CTCs and with >3 CTCs were equal - 50% (94 of 188). CTCs were not registered in 37.1% cases (111 of 299). The absence of CTCs was noted equally often in moderate and strong lymphocytic infiltration – 43.7% and 43.8%. The presence of tumor cells in the peripheral blood was most often detected in weak lymphocytic infiltration, being 1.4 times more frequent than in moderate and strong infiltration (76.5% vs. 56.3% and 56.2%) (p = 0.019, c2= 11.890). Conclusions: The study demonstrated a significant relationship between the level of CTCs and the intensity of lymphocytic infiltration in the tumor (p≤0.05), which can be used as a new prognostic approach.
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