How is Gamma Knife Radiosurgery different than standard external beam radiation therapy (radiotherapy)?
With standard external beam radiation therapy, tumors and much or all of the surrounding brain are treated with the same dose of radiation. Standard external beam radiation is given in small increments over several weeks to allow normal brain tissue to recover from the harmful effects of the external beam radiation. The brain can only absorb a certain dose of radiation, beyond which no further treatment is advisable. Gamma Knife Radiosurgery, on the other hand, allows radiation to be largely confined to the target (e.g. a brain tumor) itself and little radiation reaches the surrounding brain. The treatment is given in one session, not in fractions over a period of days or weeks, as is the case for external beam radiation. Finally, if the tumor re-grows, or new tumors appear, patients can be retreated with radiosurgery. Usually patients cannot be retreated by radiotherapy.
