PROSPECTS OF THE USE OF MELATONIN IN RADIATION THERAPY

Abstract

Summary. Radiation therapy (RT) plays a key role in the treatment of malignant tumor diseases in the majority of cancer patients. Unfortunately, despite the improvement of RT methods and tools (in particular, its conformal strategy) and modern methods of dosimetry, RT has a harmful effect not only on the tumor, but also on normal tissues surrounding the tumor. In some cases, this leads to the development of radiation reactions and complications, the treatment of which is a long, sometimes ineffective process. One of the strategies to prevent or reduce these complications is the use of natural radioprotectors, among which the pineal hormone melatonin deserves attention. It is a powerful antioxidant with immunoregulatory properties that can reduce toxicity caused by ionizing radiation (IR) in various organs. These effects are mediated by the modulatory effects of melatonin at different levels of tissue response to IR. The most important are the effects on the DNA repair system, antioxidant enzymes, immune cells, cytokine secretion, transcription factors and protein kinases. The data highlighted in this review indicate that melatonin has great potential to prevent the side effects of RT and its inclusion as an adjuvant in RT would enable the use of higher radiation doses in treatment. In addition, due to the antitumor and radiosensitizing properties of melatonin, its use can increase tumor damage. Therefore, melatonin is a promising radioprotective agent of normal tissues surrounding the tumor with the effect of increasing the therapeutic efficiency/toxicity ratio of chemoradiation treatment of patients.