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How does radiation therapy destroy cancer cells?

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linear accelerator; external beam radiation therapy — radiation therapy External beam radiation therapy (also known as external beam teletherapy, or long-distance therapy) being delivered using a machine known as a linear accelerator.

Radiation therapy destroys cancer cells primarily by damaging their DNA within the cell nucleus. This process utilizes ionizing radiation—such as X-rays, gamma rays, or particle beams—which deposits energy into tissues.12

This energy causes damage through two main mechanisms:
* Direct damage: The radiation directly disrupts the molecular structure of the DNA.1
* Indirect damage: The radiation interacts with tissue to produce free radicals and oxidants, which subsequently break or damage the DNA.2

Because cancer cells are typically more radiosensitive than healthy cells, they are particularly vulnerable to this genetic injury. When the DNA is damaged beyond the cell's ability to repair it, the cancer cells lose their capacity to replicate and eventually die. This process is most effective when cells attempt to divide, as the accumulated lesions in their chromosomes prevent successful division, leading to cell death and the regression of the tumor.31