Radiotherapy (RT) is one of the major methods of
cancer treatment. RT destroys
cancer cells, but also affects the tumor microenvironment (TME). The delicate balance between
immunomodulation processes in TME is dependent, among other things, on a specific radiation dose. Despite many studies, the optimal dose has not been clearly determined. Here, we demonstrate that
brachytherapy (contact
radiotherapy) inhibits
melanoma tumor growth in a dose-dependent manner. Doses of 10Gy and 15Gy cause the most effective
tumor growth inhibition compared to the control group.
Brachytherapy, at a single dose of ≥ 5Gy, resulted in reduced
tumor blood vessel density. Only a dose of 10Gy had the greatest impact on changes in the levels of
tumor-infiltrating immune cells. It most effectively reduced the accumulation of protumorogenic M2 tumor-associated macrophages and increased the infiltration of cytotoxic CD8+ T lymphocytes. To summarize, more knowledge about the effects of irradiation doses in anticancer
therapy is needed. It may help in the optimization of RT treatment. Our results indicate that a single dose of 10Gy leads to the development of a robust immune response. It seems that it is able to convert a tumor microenvironment into an "in situ"
vaccine and lead to a significant inhibition of
tumor growth.