SBRT is a specialized, technologically advanced type of external beam radiation therapy that pinpoints high doses of radiation directly on the cancer. Because of high precision, these treatments spare healthy tissue and are associated with fewer side effects. SBRT is very different from conventional therapy where radiation is delivered in small doses given daily over the course of several weeks. For SBRT, the total dose of radiation is typically administered in 4-5 daily sessions. SBRT can be delivered with standard, so called photon radiation, or proton beam. Neither of these two types of radiation is generally superior over the other. There are technical differences between these two, and depending on tumor location, size, shape, and other factors, the investigators will decide which type of radiation to use for which treatment.