Changes of immune status in patients with different PD-L1 expression after stereotactic body radiation therapy of oligometastasis

Abstract

Purpose. To study the influence of PD-L1 expression on the dynamics of immunological changes before and at different intervals after stereotactic body radiation therapy (SBRT) of metastatic lesions in patients with metastatic forms of solid tumors. Materials and methods. A quantitative assessment and analysis of blood immunological parameters was conducted before irradiation, via 3-4 weeks and via 6-8 weeks after SBRT in patients with malignant tumors with oligometastases in the liver or lungs, in groups with negative and positive expression of PD-L1. All peripheral blood samples were analyzed by flow cytometry. Statistical analysis was performed using Friedman and Nemenyi criteria. Results. 3-4 weeks after the end of SBRT in group CPS <1 we observed statistically significant increase of activated T-helpers (CD3+CD4+HLA-DR+), activated cytotoxic T-lymphocytes (CD3+СD8+HLA-DR+), T-lymphocytes (CD3+CD19-) and T-helpers (CD3+CD4+). Wherein, activated T-helpers and activated cytotoxic T-lymphocytes statistically significantly increased 6-8 weeks after SBRT compared with the study before irradiation. In group CPS> 1, we revealed statistically significant increase of activated T-helpers 6-8 weeks after and decrease of T-regulatory lymphocytes (CD4+CD25brightCD127low) 3-4 weeks after completion of SBRT compared with the study before radiotherapy. When we analyzed the indicators by the TPS index, most of the statistically significant changes were recorded in the group with negative expression (TPS <1): increasing of activated T-helpers and activated cytotoxic T-lymphocytes 3-4 weeks and 6-8 weeks after SBRT and decreasing of T-regulatory lymphocytes 3-4 weeks after irradiation compared with the study before irradiation. Conclusion. Groups with negative PD-L1 expression (CPS <1 and TPS <1) are associated with a more activated antitumor T-cell immune response compared to patients with positive PD-L1 status (CPS≥1 and TPS≥1), however, further researches are needed.