How does something like radiotherapy treat prostate cancer?

How does something like radiotherapy treat prostate cancer?

There are three ways of using radiotherapy: one is something called x-ray beam radiotherapy where x-rays are fired at a target. Another way is brachytherapy where a radioactive source is put in a tumour, and the third way is injecting a radioactive substance like radioactive iodine, which treats thyroid cancer. The reason it destroys the cancer is due to the way the radioactivity interacts with cells and causes DNA damage. It's specifically the ionising radiation that we use because the interaction with the cell causes electrons to be given off and leaving cells that are ionised. Usually when x-rays or gamma rays interact with the body, they actually interact with water and that water can form free radicals. The free radicals can cause damage to the cells by damaging the DNA.