Mayo Clinic’s Arizona campus is the best hospital in Arizona according to U.S. News & World Report. Mayo Clinic's state-of-the-art Proton Beam Therapy Program in Phoenix, Arizona delivers the best possible, precise radiotherapy with lower doses of radiation to healthy tissue. This highly targeted therapy is ideal for people with tumors close to or in vital organs and for young people, whose organs are still developing. The Mayo Clinic Proton Beam Therapy Program uses the latest form of proton beam therapy — pencil beam scanning. Mayo Clinic offers proton beam therapy at its Arizona and Minnesota campuses.