What is the mechanism by which radiation therapy treats cancer?

Radiation therapy primarily operates through the mechanism of damaging the DNA of cancer cells. When radiation is administered, it leads to the formation of free radicals and ionization, which can cause breaks in the DNA strands. This damage disrupts the cancer cell's ability to replicate and function properly. If the damage is extensive and overwhelms the cell’s ability to repair it, the cell will undergo apoptosis, or programmed cell death.

This selective targeting of rapidly dividing cells makes radiation therapy particularly effective against cancer, as these cells are generally more vulnerable to DNA damage compared to normal, healthy cells that may divide at a much slower rate or have more robust repair mechanisms. By impairing the genetic integrity in cancer cells, radiation therapy effectively inhibits tumor growth and diminishes the mass or spread of cancerous tissues.

In contrast, mechanisms such as enhancing metabolic activity, targeting the immune system, or increasing blood flow to tumors do not directly reflect how radiation therapy works in terms of its primary method of action against cancer cells.