Proton therapy is a type of radiation therapy; a treatment that uses high-energy beams to treat tumors.Radiation therapy using X-rays has long been used to treat cancers and noncancerous (benign) tumors. Proton therapy is a newer type of radiation therapy that uses energy from positively charged particles called protons.Proton therapy has shown promise in treating several kinds of cancer. Research of proton therapy continues, as doctors try to determine who may benefit from proton therapy treatment.Proton therapy isn't widely available in the United States.