Proton beam therapy delivers radiation therapy using particles instead of an X-ray beam. The benefit of proton therapy is that there is little to no radiation dose beyond the treatment area. This means that your doctor may be able to decrease dose to the surrounding healthy brain, which could lead to fewer side effects during or after completion of radiotherapy. Proton therapy also may allow delivery of radiation a second time or a higher total dose of radiation for certain tumors. This treatment is not yet widely available throughout the United States.