Effect of Radiotherapy on Antitumor Immune Response in Breast Cancer Patients

Radiotherapy induces tumor cell death through DNA damage. Direct relationship between radiation therapy and the immune system is responsible for many of the antitumor effects of radiotherapy. The effects of radiation therapy extend beyond direct cytotoxicity on tumor cells to additional systemic antitumor effects. The objective of this study was to evaluate the effect of radiotherapy on the circulating levels of tumor necrosis factor-α (TNF-α), Interferon-gamma (IFN-γ), CD8+ cytotoxic T lymphocytes and CD56+ natural killer cells in breast cancer patients. This study included 90 women divided into two main groups: Group I: 45 patients with stage II-III invasive breast carcinoma, group II: 45 healthy women as a control group. All studied patients received adjuvant radiotherapy after surgery. Enzyme-linked immunosorbent assay provided the measurement of TNF-α and INF-γ. Flow cytometry assessed the levels of CD8+ cytotoxic T lymphocytes and CD56+ natural killer cells. A significant reduction occurred in the percent of CD8+ and CD56+ cells in breast cancer patients after radiotherapy. There was a significant increase in both TNF-α and INF-γ in the plasma of breast cancer patients after radiotherapy. TNF-α and INF-γ cytokines significantly increased while the percent of CD56+ and CD8+ cells significantly decreased following exposure to radiotherapy. Such immune modulatory potential and increase in the knowledge of radiation induced out of field and systemic effects, foresee a rapid progress in the development and clinical application of new combined radiotherapeutic and immunotherapeutic approaches.