*1.1.2 Adverse effects of RT*

Toxicity resulting from exposure to ionizing radiation is very common [1, 2]. Considering that some healthy tissues, including the skin and mucous membranes, have a high proliferation capacity, fractioned doses also reach these tissues, promoting adverse reactions [1].

Adverse effects of RT are characterized by reactions that occur in tissues adjacent to the tumor or in contact with ionizing radiation during dose administration. These adverse effects can be acute or chronic, depending on the time of onset [7].

Acute adverse effects appear during RT or up to 3 months after completion in tissues with a high proliferation capacity [3, 4, 7]. For example, tissues such as the skin and mucous membranes are frequently affected [3, 4, 7]. The chronic effects appear from 3 months after the end of RT to years later, affecting tissues composed of cells with lower proliferation capacity such as cardiac, muscular, and subcutaneous tissue [3, 4, 7, 12].

Depending on the severity of the acute reactions, treatment may need to be interrupted [7]. These reactions cause pain and discomfort and may negatively impact patients' quality of life [3].
