Understanding Radiation Therapy
Brachytherapy is the most common type of internal radiation therapy. It is used to treat some types of cancer, including breast, cervical, prostate and uterine. As with external beam radiation therapy, the main treating specialist for brachytherapy is a radiation oncologist. How you have brachytherapy may vary between hospitals. The general process is described below, but your treatment team can give you more specific information.
How brachytherapy works
In brachytherapy, sealed radioactive sources are placed inside the body, close to or inside the cancer. The sources produce gamma rays, which have the same effect on cancer as the x-rays used in external beam radiation therapy, but act over a short distance only. It is a way of giving a high dose of radiation to the cancer with a very low dose to surrounding tissues and organs.
The type of brachytherapy used depends on the type of cancer. It may include seeds, needles, wires, pellets or small mobile sources that move from a machine into the body through applicators (thin plastic tubes). Brachytherapy may be used alone or with external beam radiation therapy.
The radiation oncologist will explain the treatment process and tell you whether you can have treatment during a day visit (outpatient) or will need a short stay in hospital (inpatient). You will have tests and scans to help your team decide where to place the radioactive sources and to work out the correct dose to deliver to the cancer. These tests may include an ultrasound, CT scan and/or MRI scan. The radiation oncologist will explain possible side effects and discuss any safety precautions. For some cancers, imaging tests, planning and treatment may all occur in the same session.
Depending on the type of brachytherapy you are having, you may need to have a local anaesthetic to numb the area being treated, or a general anaesthetic so you will be unconscious for the treatment. The radiation sources will be positioned in your body, sometimes with the help of imaging scans (such as x-ray, ultrasound and CT) and computerised machines.
You should not have any severe pain or feel ill during a course of brachytherapy. If the radioactive sources are being held in place by an applicator, you may feel some discomfort, but your doctor can prescribe medicine to help you relax and relieve any pain. Once the applicator is removed, you may be sore or sensitive in the treatment area. After the treatment, you may have to limit physical and sexual activity and take some safety precautions for a period of time – your treatment team will advise you.
If you need to stay in hospital for treatment, take reading material and other activities to keep you occupied. You may also be able to watch television or listen to music. Check with your doctor what you can take into the room, as there may be restrictions.
You may be told you are having high-dose-rate, low-dose-rate or pulsed-dose-rate brachytherapy.
high-dose-rate (HDR) – Uses a single source that release high doses of radiation in short sessions, each lasting a number of minutes. The source is removed at the end of each session.
low-dose-rate (LDR) – Uses multiple sources or seeds that release radiation over days, weeks or months. The sources may be temporary or permanent.
pulsed-dose-rate (PDR) – Uses a single source that release radiation for a few minutes every hour over a number of days. The source is removed at the end of treatment.
Depending on the type of cancer and your radiation oncologist’s recommendation, the radioactive sources may be placed in your body for a limited time or permanently.
In temporary brachytherapy, you may have one or more treatment sessions to deliver the full dose of radiation prescribed by the radiation oncologist. The radioactive source is inserted using applicators such as thin plastic tubes (catheters) or cylinders. The source is removed at the end of each treatment session. The applicator may be removed at the same time, or left in place until after the final session.
Temporary brachytherapy is mostly used for prostate cancers and gynaecological cancers (such as cervical and vaginal cancers).
Safety precautions – While the radioactive source is in place, some radiation may pass outside your body. For this reason, hospitals take certain safety precautions to avoid exposing staff and visitors to radiation. Staff will explain any restrictions before you start brachytherapy treatment.
In some cases, the treatment will be high-dose-rate brachytherapy and it will be given for a few minutes at a time during multiple sessions. The radiation therapists will leave the room briefly during the treatment, but will be able to see and talk to you from another room. You may be able to have this treatment as an outpatient.
In other cases, the radioactive sources will deliver low-dose-rate or pulsed-dose-rate brachytherapy over 1–6 days. During this time, you will be an inpatient and will stay alone in a dedicated treatment room within or close to the main hospital ward.
For low-dose-rate or pulsed-dose-rate brachytherapy, hospital staff will only come into the room for short periods of time, and visitors may be restricted – children under 18 and pregnant women are usually not allowed to enter the room. You can use an intercom to talk with staff and visitors outside the room.
If you have temporary brachytherapy, once the source is removed, you are not radioactive and there is no risk to other people.
In permanent low-dose-rate brachytherapy, radioactive seeds about the size of an uncooked grain of rice are put inside special needles and implanted into the body while you are under general anaesthetic. The needles are removed, and the seeds are left in place to gradually decay.
As the seeds decay, they slowly release small amounts of radiation over weeks or months. They will eventually stop releasing radiation, but they will not be removed. Low-dose-rate brachytherapy is often used to treat early-stage prostate cancers.
Safety precautions – If you have permanent brachytherapy, you will be radioactive for a short time after the seeds are inserted. The radiation is usually not strong enough to be harmful to people around you, so it is generally safe to go home. However, you may need to avoid close contact with young children and pregnant women for a short time – your treatment team will advise you of any precautions to take. You will normally be able to return to your usual activities a day or two after the seeds are inserted.
For some cancers, you may be referred to a nuclear medicine specialist to have another type of internal radiation therapy.
Radionuclide therapy – Also known as radioisotope therapy, this involves radioactive material being taken by mouth as a capsule or liquid or given by injection. The material spreads throughout the body, but particularly targets cancer cells. It delivers high doses of radiation to kill cancer cells with minimal damage to normal tissues.
Different radionuclides are used to treat different cancers. The most common radionuclide therapy is radioactive iodine, which is taken as a capsule and used for thyroid cancer.
Other radionuclide therapies include:
- peptide receptor radionuclide therapy (PPRT), which uses a small amount of a radioactive substance that has been combined with a cell-targeting protein (peptide). PPRT is used to treat neuroendocrine tumours (NETs) of the bowel, pancreas and lung; and some advanced prostate cancers
- injection with a small amount of bone-seeking radioactive liquid to target cancer that has spread to the bone
- injection of radioactive antibodies to treat lymphoma.
SIRT – Also known as radioembolisation, SIRT stands for selective internal radiation therapy. This method delivers high doses of radiation to cancers in the liver. It uses tiny pellets called microspheres, which contain a radioactive substance. The pellets are injected into a thin tube called a catheter, which is inserted into the main artery (hepatic artery) that supplies blood to the liver.
Radiation from the microspheres damages the cancer cells and their blood supply. This means the cancers can’t get the nutrients they need and they shrink.