Stereotactic Ablative Radiotherapy Induces Systemic Differences in Peripheral Blood Immunophenotype Dependent on Irradiated Site

We performed a prospective study to assess the systemic immune response 1–2 weeks following stereotactic radiation (SAR) to different organs using flow cytometry for immunophenotyping and Luminex analysis. Our results suggest SAR to parenchymal sites (lung and liver) induces systemic immune changes, including a decrease in total and cytotoxic NK cells and an increase in TIM-3+ NK cells and activated memory CD4+ and CD8+ T cells. SAR to non-parenchymal sites did not induce these changes.