Radio Therapy, or Radiation Oncology, (in the UK, Canada and Australia), Radiation Therapy (in the USA) sometimes abbreviated to XRT, is the medical use of ionizing radiation as part of cancer treatment to control malignant cells (not to be confused with radiology, the use of radiation in medical imaging and diagnosis). Radiotherapy may be used for curative or adjuvant treatment. It is used as palliative treatment (where cure is not possible and the aim is for local disease control or symptomatic relief) or as therapeutic treatment (where the therapy has survival benefit and it can be curative). Total body irradiation (TBI) is a radiotherapy technique used to prepare the body to receive a bone marrow transplant. Radiotherapy has several applications in non-malignant conditions, such as the treatment of trigeminal neuralgia, severe thyroid eye disease, pterygium, pigmented villonodular synovitis, prevention of keloid scar growth, and prevention of heterotopic ossification. The use of radiotherapy in non-malignant conditions is limited partly by worries about the risk of radiation-induced cancers.

Radiotherapy is used for the treatment of malignant cancer, and may be used as a primary or adjuvant modality. It is also common to combine radiotherapy with surgery, chemotherapy, hormone therapy, Immunotherapy or some mixture of the four. Most common cancer types can be treated with radiotherapy in some way. The precise treatment intent (curative, adjuvant, neo adjuvant, therapeutic, or palliative) will depend on the tumor type, location, and stage, as well as the general health of the patient.

Radiation therapy is commonly applied to the cancerous tumor. The radiation fields may also include the draining lymph nodes if they are clinically or radio logically involved with tumor, or if there is thought to be a risk of sub clinical malignant spread. It is necessary to include a margin of normal tissue around the tumor to allow for uncertainties in daily set-up and internal tumor motion. These uncertainties can be caused by internal movement (for example, respiration and bladder filling) and movement of external skin marks relative to the tumor position.

Types of Radiation Therapy:

• External Beam Radiotherapy
• Conventional External Beam Radiotherapy
• Stereo tactic Radiation
• Virtual Simulation, 3-dimensional conformal radiotherapy, and intensity-modulated radiotherapy
• Particle Therapy
• Brachytherapy
• Radioisotope Therapy (RIT)