Radiotherapy uses high-energy rays to treat cancer. It destroys tumour cells in the area being treated. Normal cells can also be damaged by radiotherapy. They can usually repair themselves, but the tumour cells can’t.
Standard radiotherapy is given using a machine called a linear accelerator (linac). This is similar to a large x-ray machine. It gives beams of radiation to the area that needs treatment. You usually have this type of radiotherapy as a series of short daily sessions over a few weeks.
SRT can be given using some linac machines, or by other radiotherapy systems such as Gamma Knife™ or CyberKnife™. Many small, thin beams of radiation are directed from different angles and cross at the tumour. The tumour itself receives a high dose of radiation. But nearby areas are only affected by the individual low-dose beams. This lowers the risk of damage to normal cells and can sometimes reduce side effects.
SRT can be given as two to eight sessions or as a single treatment (this is called stereotactic radiosurgery). SRT is sometimes given over five to six weeks, like standard radiotherapy.