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Systemic radiation therapy

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.

Sources of radiation

The radioactive isotopes used for systemic radiation therapy include:

  • iodine
  • strontium
  • phosphorus

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.

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Delivering systemic radiation therapy

The radioactive materials may be delivered in the following ways:

  • by mouth (orally)
    • The radioactive material is given by mouth (orally) in the form of a capsule or a drink.
    • For example, radioactive iodine (I-131) is used to treat some types of thyroid cancer. The thyroid uses iodine to make hormones. The thyroid and thyroid cancer cells absorb the radioactive iodine. The radiation in the iodine is toxic to the cancer cells and destroys them.
  • intravenous injection
    • The radioactive material is injected into a vein.
    • For example, strontium-89 (Sr-89, Metastron) may be used to help relieve pain in cancers that have spread (metastasized) to the bone. The injected material is absorbed by areas of the bone containing cancer. The radiation kills cancer cells and relieves bone pain.
  • instillation
    • The radioactive material is placed in, or instilled into, a body cavity or space.
    • For example, phosphorus-32 (P-32) can be instilled into the abdominal cavity or, less commonly, into the thin layer of tissue that covers the lungs (pleura). Phosphorus-32 can reduce a buildup of fluid in these areas, a side effect of some types of advanced cancer.

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Planning systemic radiation therapy

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.

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Preparing children for systemic radiation therapy

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.

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Getting systemic radiation therapy

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.

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Safety measures

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.

Precautions while in 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.

  • time
    • Time limits may be placed on visiting to reduce exposure. Time limits vary (such as 10–30 minutes per day) and are determined on an individual basis.
    • The amount of time nursing staff spends with a person with a radioactive implant is limited to minimize their exposure.
  • distance
    • Radiation levels are highest at the radioactive source. They become weaker farther away from the source.
    • Visitors may be asked to stay at least 6 feet from a person receiving brachytherapy or systemic radiation therapy.
    • Nursing staff may speak to the person from the doorway or through an intercom.
  • shielding
    • Portable lead shields or other protective devices may be placed between the person receiving radiation therapy and the visitor or caregiver.
  • Rooms in which radiation therapy is given are specially shielded, so there is no risk of exposure to anyone outside these rooms. People receiving radioactive isotopes, such as radioactive iodine, may have to follow safety precautions related to body fluids for a few days. This is because the radioactive material is passed from the body through urine and other body fluids. Safety precautions include:
    • Sit on the toilet to urinate to prevent splashing.
    • Flush the toilet 2–3 times each time you urinate or have a bowel movement.
    • Wipe up any spilled urine with a tissue and flush it down the toilet.
    • Wash hands immediately after using the toilet.
    • Use disposable dishes and cutlery.
  • Linen and garbage are kept in containers in the room until the treatment is completed.

Precautions at home

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:

  • Sit on the toilet to urinate to prevent splashing.
  • Flush the toilet 2–3 times each time you urinate or have a bowel movement.
  • Wipe up any spilled urine with a tissue and flush it down the toilet.
  • Wash hands immediately after using the toilet.
  • Wash clothing and linens that are stained with urine or blood as soon as possible. Wash these items apart from other laundry and rinse thoroughly.
  • If you cut yourself, wash away any spilled blood.
  • Use disposable dishes and cutlery.

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Researcher Dr Trang Hoang Dr Trang Hoang is targeting resistant cells in childhood leukemia.

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