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Systemic radiation therapy is a type of radiation therapy in which radioactive material travels through the bloodstream to reach cells all over the body. Systemic radiation is used to treat certain types of cancer, such as thyroid cancer, or to relieve pain when cancer has spread (metastasized) to the bone. It is also called unsealed internal radiation therapy, radioisotope therapy, radionuclide therapy or radiopharmaceutical therapy.
The radioactive isotopes used for systemic radiation therapy include:
The time it takes for half of a material’s radioactivity to disappear is called the half-life. Different radioactive materials have different half-lives. This information helps the radiation therapy team to choose the type of material to use and plan the treatment regimen. It also determines how long radiation safety precautions must be taken following treatment.
The radioactive materials may be delivered in the following ways:
The radiation therapy team reviews laboratory and imaging tests before systemic radiation therapy begins. Special preparation may be needed, depending on the type of cancer being treated. Also, the healthcare team must confirm that women of child-bearing age are not pregnant or breastfeeding. Breastfeeding is stopped about 1–2 weeks before systemic radiation therapy is given.
The dose of systemic radiation treatment is different for each person. It will depend on the type of cancer being treated, the radioactive source used and, in some cases, body weight.
Receiving radiation therapy can be a frightening experience if children don’t know what is happening to them. Because they are frightened, children may not want to or can’t cooperate during the treatment process. Helping children understand what is happening and preparing them for treatment will reduce their fears and will allow them to work with the radiation therapy team.
Special preparation for systemic radiation therapy may be needed, depending on the type of cancer being treated. Also, the healthcare team must confirm that girls of child-bearing age are not pregnant and are not breastfeeding. Breastfeeding is stopped 1–2 weeks before systemic radiation therapy is given.
Systemic radiation therapy is given in a hospital (usually the nuclear medicine department) or cancer treatment centre. The person receiving systemic radiation therapy is usually admitted to the hospital, but sometimes the treatment can be given on an outpatient basis. This depends on the area being treated, the type of systemic radiation therapy and the person’s overall health.
The radioactive isotope (also called a radiopharmaceutical) is given orally (by mouth), injected intravenously (directly into the vein) or instilled into a body cavity or space. The radioactive isotope travels to and is absorbed by cancer cells in certain parts of the body. One dose is usually all that is needed.
People receiving systemic radiation therapy usually stay in a private room in the hospital or treatment centre while the radiation is most active (usually for about 48–72 hours). The length of time depends on the type and dose of radioactive isotope used. For example, most people who receive radioactive iodine (I-131) need to stay in hospital, but some people can receive treatment as outpatients if they are given lower doses.
While the radiation is most active, some is detectable outside the body. Safety precautions are necessary to protect other people at the hospital and visitors from radiation. The radioactive isotope becomes less radioactive each day. Although radiation in the body is very weak by the time people are discharged from hospital, they may need to take some safety precautions at home. The radioactive material is eventually used up over several days or weeks.
People receiving internal radiation are usually admitted to a private room and isolated from other people in the hospital. This can be a difficult time because of restrictions placed on visiting and nursing care. Some activities may also be restricted, but the person receiving treatment can usually still read, watch television, listen to music or talk on the telephone. Nursing staff will provide all the care needed.
A radiation physicist may regularly measure the level of radioactivity in the room. They may also measure radioactivity in people receiving radiation therapy before they are discharged from the hospital.
The length of time that precautions need to be taken varies with the type of systemic therapy used, but it is usually about 2–3 days.
A sign is placed on the door asking visitors to report to the nurse’s station before entering the room. This is done so visitors can be made aware of any precautions they need to take. Children under the age of 18 and pregnant women are not allowed in the room while the radiation source is active.
Precautions are based on some of the following principles.
The radiation therapy team will give people receiving systemic radiation therapy special instructions about any safety precautions they need to follow and how long they need to take these precautions. People should talk to their radiation oncologist or radiation therapy team about any safety concerns or questions they have.
Most of the radiation is gone from the person’s body within a few days after treatment, but people may still need to take precautions for a while after they return home. The healthcare team will tell people given radioactive isotopes, such as radioactive iodine (I-131) or strontium-89 (Sr-89, Metastron), any special safety precautions they need to take when they go home. They should follow these instructions until their bodies no longer contain enough radiation to be considered a hazard to others.
Safety precautions include: