144P Influence of tumor-infiltrating T-cells' characteristics on the survival of patients with primary choroid melanoma

To assess the relationship between tumor infiltrating T-cells characteristics and survival rates of patients with primary choroid melanoma. A retrospective cross-sectional study was performed on the material of 50 choroid melanoma. Inclusion criteria: enucleation as the only treatment method, availability of medical documentation and biopsy material, no distant metastasis at diagnosis. The immunohistochemical (IHC) staining of tumor samples was performed with antibodies to CD3, FoxP3. Before staining, tissues depigmentation with 10% Н2О2 was performed to improve the result visualization. The number of CD3- and FoxP3-positive cells was counted in 5 non-overlapping fields of view (×20) by two researchers. The regression analysis was used to evaluate the relationship between histological characteristics, characteristics of tumor infiltrating lymphocytes and survival rates. The study endpoints were progression-free survival and overall survival. In univariate regression analysis, the presence of FoxP3 expression worsened the prognosis for disease progression (HR 1.5 95% CI 1.4-3.5, p=0.005), but not for death from choroidal melanoma (p=0.8). When the ratio of FoxP3-positive to CD3-positive cells exceeded 0.5, the risk of progression was 2 times higher than when the fraction of FoxP3-positive cells was less than 0.5 (p=0.003). No pattern was found for overall survival. When conducting multivariate regression analysis, a statistically significant relationship with progression-free survival was identified for the pT category (HR 1.5 95% CI 1.1-3.3 p=0.04) and FoxP3/CD3 ratio more than 0.5 (HR 6.9 95%CI 1.1-20.0, p=0.04). The median progression-free survival in the FoxP3/CD3 group greater than 0.5 was 51 months, in the FoxP3/CD3 group less than 0.5 median was not reached. The fraction of FoxP3-positive cells among all tumor infiltrating T-cells has a statistically significant effect on progression-free survival in patients with choroid melanoma. With FoxP3/CD3>0.5 ratio, the risk of disease progression increased by 6.9 times (p=0.04).