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Radiotherapy with caesium or iridium

Nurse and patients talking about cancer

This page tells you about caesium or iridium internal radiotherapy treatment. This type of internal radiotherapy is called brachytherapy. There is information about


What caesium and iridium are

Caesium 137 and iridium 192 are both radioactive metals called radioactive sources. Doctors can use them to treat 

These treatments are also called caesium or iridium insertion. This page tells you about caesium and iridium insertion in women. We have detailed information about internal radiotherapy for prostate cancer in our prostate cancer radiotherapy section.


Caesium and iridium treatment in women

To give caesium or iridium treatment, doctors put applicators inside your cervix (neck of the womb) and vagina. While they do this you have a medicine to make you drowsy. The applicators are like long, thin, plastic tampons. This procedure is usually done in the operating room. When the applicators are put in, you may also have a tube (urinary catheter) put into your bladder at the same time. The diagram below shows the applicators in place for womb cancer treatment.

Diagram showing the position of the applicators for the internal radiotherapy for womb cancer

You may have an X-ray or a CT scan once the applicators are in place, to check that they are in the right position.

Once you are back on the ward, or in a specially shielded room, the nurses attach tubes from a machine to the applicators. When the machine is switched on it sends small radioactive metal balls into the applicators to treat the cancer. The applicators can be uncomfortable. Your nurse will give you regular painkillers if you need them. Let your nurse know if you are still uncomfortable so that they can change the dose of the painkiller.

Once the machine is switched on, you have to stay in bed. This helps to keep the applicators in the correct position. If you need anything you can call the nurse by using the call bell by your bed.


Internal radiotherapy machines

The treatment machines have different names, including Curietron, Selectron, and Microselectron. The machine puts the radioactive metal balls into the applicators automatically.

When someone needs to come into your room the machine can be turned off. The machine pulls the radioactive sources back through the tubes and inside the machine. So your visitors and the hospital staff won't be exposed to as much radiation. But they will still need to follow hospital safety procedures and visiting restrictions. Some hospitals use pulsed dose brachytherapy machines (PDR machines). Every hour or so your nurse connects you to a machine that gives the radiotherapy. At other times you are free to have visitors.

Internal radiotherapy may take less than an hour or up to 2 days, depending on the type of machine that is used. Some machines give a low dose over a long time and some give a high dose over a shorter time.


Low dose rate treatment

If you have low dose rate treatment, it usually takes between 12 and 48 hours, depending on how much external radiotherapy you have had. Your treatment team will plan your total radiotherapy dose and your nurses will monitor the machine to give that dose. If the machine needs to be switched off a lot, the time to give the radiotherapy will be longer.

The doctor or nurse takes the applicators out once you've had your dose of radiation. This is usually done on the ward in your side room. It can be a bit uncomfortable. You will be asked if you want to take some painkillers beforehand. Sometimes a few breaths of the gas Entonox can help you to relax.

The nurses check that all the applicators have been removed. And they take the tube draining your urine (catheter) out at the same time.


High dose rate treatment

High dose rate treatment machines have sources that give off radiation more quickly. So the treatment time is shorter. The treatment may only last between 5 and 15 minutes. But you may need up to 6 treatments, up to a week apart, with this type of machine. You usually have this treatment in combination with external radiotherapy

You have the applicators put in under general anaesthetic the first time. Or you may have medicine to make you drowsy (sedation).

In some hospitals, a small plastic cuff is left in place, in the opening of your cervix. This is a narrow plastic tube, to guide the applicators after the first treatment. If your hospital gives the treatment this way, you may not need an anaesthetic the second time around. 

After all the treatments are over, the plastic cuff is taken out. This is quick but can be a bit painful. You may want to ask for pain relief while it is done, such as gas and air (Entonox) or painkilling tablets.


After treatment

Once the radioactive sources are removed, the radioactivity disappears. You can usually go home the same, or next day.

Some doctors may suggest that you use vaginal douches to clean the vagina for a few days afterwards, but this is not common. If you have questions or concerns about douching, talk them over with your doctor or specialist nurse.

Your doctor or specialist nurse will advise you to drink plenty of fluids. This helps to flush out your bladder and stop you from getting inflammation or infection of the bladder.


Side effects

The side effects of caesium or iridium internal radiotherapy are the same as those explained in the section about the side effects of stomach and pelvic radiotherapy.

There is a small risk of infection after caesium or iridium insertion but it is rare. If you get a high temperature or heavy bleeding after your treatment, contact your doctor as soon as possible. Your doctor will probably give you antibiotics to clear up any infection.

Radiotherapy to the vaginal area can make your vagina narrower after some time. The tissue can become stiffer and less stretchy. Doctors call this fibrosis. Your doctor, nurse or radiographer will recommend that you use vaginal dilators to help stretch your vagina and prevent it from getting narrow. There is detailed information about vaginal dilators in the page about sex and cancer for women in the coping with cancer section.


More about caesium and iridium radiotherapy

We have detailed information about internal radiotherapy in this section.

You can find further information about 

There is also detailed information about the side effects of radiotherapy.

You can phone the Cancer Research UK nurses on freephone 0808 800 4040. The lines are open from 9am to 5pm, Monday to Friday. They will be happy to answer any questions that you have.

Our general organisations page gives details of people who can provide information about radiotherapy. Some organisations can put you in touch with a cancer support group. Our cancer and treatments reading list has information about books, leaflets and other resources about radiotherapy treatment.

If you want to find people to share experiences with online, you could use Cancer Chat, our online forum.

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Updated: 30 April 2014