Radiation Therapy Principles

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Internal radiation therapy (brachytherapy)

Internal radiation therapy is also known as brachytherapy, which means short-distance therapy. With this method, sources of radiation are put in or near the area that needs treatment. The radiation only travels a short distance, so there is less risk of damaging nearby normal tissues. Brachytherapy can be used to deliver a high dose of radiation to a small area in a fairly short period of time. It’s useful for tumors that need a high dose of radiation or are near normal tissues that are easily hurt by radiation.

The main types of internal radiation are:

  • Interstitial radiation: the radiation source is placed directly into or next to the tumor using small pellets, seeds, wires, tubes, or containers.
  • Intracavitary radiation: a container of radioactive material is placed in a cavity of the body such as the chest, rectum, uterus, or vagina.

Ultrasound, x-rays, or CT scans are used to help the doctor put the radioactive source in the right place. The placement can be permanent or temporary.

Permanent brachytherapy uses small containers, often called pellets or seeds, which are about the size of a grain of rice. They are put right into the tumors using thin, hollow needles. Once in place, the pellets give off radiation for several weeks or months. Because they are very small and cause little discomfort, they are simply left in place after their radioactive material is used up.

Temporary brachytherapy can be high-dose rate (HDR) or low-dose rate (LDR). Either type places cylinders, hollow needles, tubes (catheters), or fluid-filled balloons into the area to be treated that are removed after treatment. Radioactive material can be put in these containers for a short time and then removed. This may be done by hospital staff or the radioactive material can be put into the device remotely by machine.

    For HDR brachytherapy, the radiation source is put into place for a few minutes at a time, and then removed. This process may be repeated twice a day for up to a week, or once a week for a few weeks.

    For LDR brachytherapy, the radiation source stays in place for up to 7 days. To keep the implant from moving, you will need to stay in bed and lie fairly still. For this reason, you will stay in the hospital during LDR therapy.

Treatment with internal radiation

Severe pain or illness is not likely to happen while putting in radioactive implants or the catheters, devices, or tubes for temporary placement of radioactive materials. You may feel sleepy, weak, or nauseated for a short time if you get anesthesia (drugs that make you sleepy) while the implant or device is put in place. Tell the nurse if you have any unusual side effects such as burning or sweating.

Anesthesia usually is not needed to take out temporary brachytherapy implants. Most can be taken out right in your hospital room. (The room is specially shielded to contain the radioactivity and the staff use mobile shields to protect themselves while handling radioactive materials.) If you had to stay in bed during implant therapy, you might have to stay in the hospital an extra day or so after the implant is removed just to be sure you have no problems in the area where the implants were placed.

Once implants are removed, there is no radioactivity in your body. (See the section, “Safety for the patient and family” for more on this.) The doctor will tell you if you should limit your physical activity for a time. Most patients are encouraged to do as much as they can. Some people need extra sleep or rest breaks during their first days at home, but you will probably feel stronger quickly. The area that has been treated with an implant may be sore or sensitive for some time after treatment.

Radioembolization

This is a special type of internal radiation that’s now used only for cancer in the liver that can’t be surgically removed. Small radioactive beads (called microspheres) are injected into the artery that feeds the liver tumor. Brand names for these beads include TheraSphere® and SIR-Spheres®. Once infused, the beads lodge in blood vessels near the tumor, where they give off small amounts of radiation to the tumor site for several days. The radiation travels a very short distance, so its effects are limited mainly to the tumor. In some cases, it can cause ulcers in the intestine, low white blood cell counts, lung damage, or serious damage to the normal liver cells.


Last Medical Review: 10/23/2013
Last Revised: 10/23/2013