Radiotherapy Induced Dynamic Changes of Circulating Blood Immune Cell Subsets in Breast Cancer.

PURPOSE/OBJECTIVE(S) Radiotherapy (RT) as a traditional treatment for Breast cancer (BC) not only could induce local tumor cell death but also modify the tumor microenvironment to engage antitumor immune response. High level of tumor infiltrating lymphocytes, especially CD8, T helper cells and dendritic cells, have great correlation with pathological complete response in BC patients. However, there is no systematic report on the dynamic changes of circulating immune cells in BC treated with RT. We detected the systemic lymphocyte subsets in the peripheral blood before, during, and after RT of BC patients to evaluate the effects of RT on different lymphocyte subtypes. MATERIALS/METHODS BC patients treated with RT were recruited to a prospective study. Blood samples were obtained EDTA coated tubes and then centrifuged for white blood cell. The antibodies including CD11b, CD45, CD19, CD3, CD56, CD4, CD8a, CD133, HLA-DR, and FOXP3 were used to identify corresponding cell subtypes. Finally, the percentage of Lymphocytes, MDSC, DC, B cells, T cells, Treg, CD8+ T cells, CD4+ T cells, NK cells, and NKT were analyzed using flow cytometry software. The paired T-test was used to compare and analyze each cell subpopulation from Pre, Dur and End of RT. P < 0.05 was considered to be significant. RESULTS Between July 2019 and January 2020, a total of 50 BC patients treated with RT that signed consent forms and sampled at three time points (Pre, Dur, End of RT) were enrolled in this study. After RT, the ratio of CD8/CD4 (Pre vs. End mean:0.73 vs. 0.60, P = 0.04) were significantly decreased while Tregs (Pre vs. End mean:2.03 vs. 2.68, P = 0.04) were increased. Analyzing the changes of myeloid Cells, DC were shown a significant gradual increase trend (Pre vs. End mean:0.23 vs. 0.37, P < 0.0001) from baseline (mean:0.23) to during (mean: 0.33) and end (0.37) of RT. Further explore the dynamic changes of lymphocytes subtypes before and after RT under each clinical stage. In stage III patients, CD4 cells (Pre vs. Dur mean:47.62 vs. 55.64, P = 0.03) and Tregs (Pre vs. Dur mean:1.83 vs. 3.37, P = 0.01) were significantly increased during RT treatment. Whereas there were drastically reduced in CD8 cells during (Pre vs. Dur mean:36.21 vs. 30.84, P = 0.003) and after (Pre vs. End mean:36.21 vs. 29.23, P = 0.03) RT treatment. After RT treatment for stage III patients, DC were shown a significant increase trend (Pre vs. Dur mean:0.25 vs. 0.37, P = 0.02; Pre vs. End mean: 0.24 vs. 0.48, P = 0.008). For other stages, there is no significant change in immune cell subsets before and after RT. CONCLUSION Different immune cell subtypes have different sensitivity to radiotherapy. Overall, RT could induce CD8/CD4 ratio decrease, Treg and DC increase. Interestingly, Stage III Breast cancer patients are more sensitive to RT, and their immune status changes significantly during RT treatment. Although these findings need to be verified for a larger sample size, the preliminary results provide instructions for subsequent personalized and precise treatment for different individuals.