Treatment Radiotherapy

Radiotherapy uses precisely targeted high-energy rays to kill cancer cells. It does this by damaging a cell's internal components (molecules), causing the cells to commit suicide by apoptosis. When a high-energy ray hits a molecule, it can cause it to break up. This can form free radicals, which can cause further damage to the inside of the cell.

read more at http://info.cancerresearchuk.org/cancerandresearch/learnaboutcancer/treatment/radiotherapy/?a=5441