Radiation Therapy -
therapy (or radiotherapy) 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 cancer 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 a few applications in non-malignant conditions, such as the
treatment of trigeminal neuralgia, severe thyroid eye disease, pterygium,
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 tumors (cancer), and may be
used as the primary therapy. It is also common to combine radiotherapy with
surgery, chemotherapy, hormone therapy or some mixture of the three. Most
common cancer types can be treated with radiotherapy in some way. The precise
treatment intent (curative, adjuvant, neoadjuvant, therapeutic, or palliative)
will depend on the tumour type, location, and stage, as well as the general
health of the patient.
Radiation therapy is commonly applied to the cancerous tumour. The radiation
fields may also include the draining lymph nodes if they are clinically or
radio logically involved with tumour, or if there is thought to be a risk of
subclinical malignant spread. It is necessary to include a margin of normal
tissue around the tumour 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 tumour position.
To spare normal tissues (such as skin or organs which radiation must pass
through in order to treat the tumour), shaped radiation beams are aimed from
several angles of exposure to intersect at the tumour, providing a much larger
absorbed dose there than in the surrounding, healthy tissue.