Why can radiation treatment slow or stop the growth of cancer cells?

Radiation therapy slows or stops the growth of cancer cells by utilizing ionizing radiation—such as X-rays, gamma rays, or particle beams—to damage the genetic material within the cell nucleus.12

This process works through two primary mechanisms:
* DNA Damage: Radiation causes breaks in the double-stranded DNA molecule. When this damage is severe, the cells cannot replicate, leading to their death.12
* Apoptosis: Radiation can induce apoptosis, or programmed cell death, effectively eliminating the malignant cells.2

Cancer cells are particularly vulnerable to this treatment because they are continuously proliferating. Unlike healthy cells, which are not always reproducing and have more robust recovery mechanisms, cancer cells are less able to repair the radiation damage they sustain. By preventing replication and triggering cell death, radiation therapy can slow the progression of malignant disease or cause a tumor to regress.21