Radiation induced lymphopenia - a possible critical factor in current oncological treatment.

Background: The effect of ionizing radiation on the immune system during the treatment of malignant tumors has long remained a point of great interest. This issue is currently gaining importance, especially in connection with the advancing development and availability of immunotherapeutic treatment. During cancer treatment, radiotherapy has the ability to influence the immunogenicity of the tumor by increasing the expression of certain tumor-specific antigens. These antigens can be processed by the immune system, stimulating the transformation of naïve lymphocytes into tumor-specific lymphocytes. However, at the same time, the lymphocyte population is extremely sensitive to even low doses of ionizing radiation, and radiotherapy often induces severe lymphopenia. Severe lymphopenia is a negative prognostic factor for numerous cancer dia-gnoses and negatively impacts the effectiveness of immunotherapeutic treatment.

Aim: In this article, we summarize the possible influence of radiotherapy on the immune system, with a particular emphasis on the impact of radiation on circulating immune cells and the subsequent consequences of this influence on the development of cancer.

Conclusion: Lymphopenia is an important factor influencing the results of oncological treatment, with a com-mon occurrence during radiotherapy. Strategies to reduce the risk of lymphopenia consist of accelerating treatment regimens, reducing target volumes, shortening the beam-on time of irradiators, optimizing radiotherapy for new critical organs, using particle radiotherapy, and other procedures that reduce the integral dose of radiation.