Radiation induces DNA damage, leads to cell cycle arrest and cell death. We investigated the effect of adjuvant radiation therapy (RT) on systemic innate and adaptive immune cells in female breast cancer (BC) patients by assessing circulating white blood cells (WBCs) and its subpopulations.
Peripheral blood cell numbers from BC patients (n = 114, median age 64) who received adjuvant RT (50 Gy) at Dept. Oncology, Ryhov hospital, Sweden, were analyzed. Blood (30 ml) was obtained from BC patients before and after adjuvant RT. The number of total WBCs and its subpopulations were analyzed by Sysmex XE5000 instrument. The phenotype of ex vivo fresh peripheral white blood cell subpopulation were analyzed by BD FACSCanto II flow cytometer and BDFACSDiva software program. Paired T-test was used for comparison between the patients before and after adjuvant RT, Significant p-values <0.05.
1. After adjuvant RT, the number of WBCs, neutrophils and lymphocytes were significantly decreased 2. Neutrophil to lymphocyte ratio (NLR) is suggested to be a biomarker for poor prognostic and short survival time for cancer patient. Interestingly, the NLR was significantly increased after treatment, p-values = <0.001. 3. As for total lymphocytes, adjuvant RT decreased the numbers in all T-cell subpopulations studied (CD3+, CD4+, CD8+, and CD3 + 56 + [NKT cells]) and in CD56 + (NK cells).
Our results indicated that adjuvant RT of BC patients induces systemic alterations in number of innate and adaptive immune cells. This might be due to the bystander or distant immunosuppression from adjuvant radiation. Alternative, adaptive and innate immune response cells are redistributed from circulation to the radiation site. The significance of these alteration on clinical outcome need further investigation.
Regional Ethical Review Board of Linköping
Clinical Cancer Research in Jönköping and Futurum, Ryhov Hospital, Jönkoping Sweden
All authors have declared no conflicts of interest.