Radiation external
External radiation therapy, also known as external beam radiation or teletherapy, is used in the treatment of cancer to deliver high levels of radiation externally to a specific area of the body. The goal of this therapy is to destroy malignant cells, which are more sensitive to radiation than normal cells, without permanently damaging adjacent body tissues. Radiation is thought to destroy the cancer cells’ ability to grow and multiply by either decreasing the rate of mitosis or impairing the synthesis of deoxyribonucleic acid or ribonucleic acid.
External radiation therapy may be used as part of cancer treatment aimed at curing the patient, or it may be used as a palliative measure in terminal cancer to relieve pain and enhance the patient’s quality of life. This therapy is most commonly given on an outpatient basis unless the patient’s underlying condition warrants hospitalization.
Curative radiation therapy is generally given 15 to 20 minutes per day 5 days per week for 4 to 8 weeks; palliative radiation therapy is usually given for less time. The dosage and the body areas receiving the beam of rays are determined by the radiation oncologist and marked on the patient’s body with tiny tattoos at the beginning of therapy.
Recent advances in external radiation therapy include large-field, large-dose radiation. Half-body treatment in which half of the body is used as a large field to receive large doses of radiation is an example of this type of external radiation. This type of therapy provides an effective, well-tolerated treatment in metastatic disease.
Total skin electron therapy, another advancement, provides radiation to the entire skin surface and has been successful in managing extensive skin disease. Hyperfractionation is an experimental type of radiation therapy that delivers more than one treatment per day in an attempt to improve tumor control.
Procedure
The patient is taken to the hospital’s radiation department, where he changes into a patient gown. He is then placed on the treatment table or floor (in the case of large-dose radiation) and told to lie immobile while a large machine, usually overhead, directs radiation at the target site for the prescribed period of time, usually 1 to 2 minutes.
Complications
Because external radiation therapy destroys normal cells in the path of the radiation beam, most patients experience some degree of skin reaction at the irradiated site. Anorexia, fatigue, and bone marrow suppression, which increases the patient’s risk of bleeding or infection, also occur. Other complications are site specific and generally related to dysfunction or change in the structure of body parts within the irradiated area. For example, alopecia may occur when the scalp is irradiated; stomatitis and esophagitis, when the head and neck are irradiated; pneumonitis, pericarditis, and upper GI distress, when the thoracic area is irradiated; and lower GI and genitourinary problems, when the abdominopelvic area is irradiated. (See Managing adverse effects of radiation therapy.)
Managing adverse effects of radiation therapy
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