Radiation Therapy is a type of treatment that uses high energy x-rays, electron beams or radioactive isotopes to create sufficient damage to the chromosomes and DNA of a cancerous cell in order to either kill or arrest its growth. A radiation oncologist (physician who specializes in radiation cancer treatment) may also use this treatment to shrink a tumor before surgery, or to relieve symptoms caused by its presence.

Depending upon the nature and stage of a tumor, radiation therapy may be used as the primary form of treatment, or in partnership (adjuvant) with other methods, such as chemotherapy or surgery.

Radiation Oncology Group uses three clinically proven types of therapy: 
External Beam Radiation
High Dose Rate (HDR) Brachytherapy
Prostate Seed Implantations
3D Conformal Therapy
Intensity Modulated Radiation Therapy (IMRT)