Radiotherapy is the use of high-energy rays to cure or control cancer; it's a very common cancer treatment in Ireland and worldwide. Find out exactly what radiotherapy is, how it works, and what the treatment involves from a patient perspective, including side effects.

This video tells you all about radiotherapy. The information in this video was correct as of 1st August 2012.

What is radiotherapy?

The beams of radiation in radiotherapy are more powerful than ordinary X-rays. They aim to destroy the cancer cells with as little damage as possible to normal cells.

  • Radiotherapy can be given on its own or with surgery, chemotherapy, hormone therapy or monoclonal antibody therapy. It can be given before surgery to shrink the tumour or after surgery to treat any residual disease.
  • Radiotherapy can be given from outside the body (externally) or from inside (internally).
  • Radiotherapy in general is safe. Depending on the type of radiotherapy, you may need to take special precautions after treatment.
  • Radiotherapy may cause side effects that can last for a short or a longer period.

When you may need radiotherapy

Your doctor may prescribe radiotherapy to destroy the tumour: this is called curative radiotherapy. You may also have radiotherapy to relieve symptoms (like pain): this is called palliative radiotherapy.

Radiotherapy can be given before or after surgery. When it is given before surgery, it is called neo-adjuvant therapy. When given after, it can prevent any cancer cells left in your body from growing, and is called adjuvant therapy.

You can get radiotherapy in special cancer treatment centres. The radiotherapy unit may not be located in the hospital where you receive your cancer diagnosis. As a result, you may have to travel to a special radiotherapy centre for treatment. We may be able to help you with the costs of your travel expenses.

Types of radiotherapy

There are different ways to give radiotherapy. It can be given from outside the body (externally) or from inside (internally). Sometimes both are used to treat cancer, for example, in the breast or prostate gland.

External beam radiotherapy

Giving radiotherapy externally is called external beam radiotherapy and a course can last 4–8 weeks. The rays come from a machine called a linear accelerator or other machines called cobalt. The different types of external beam radiotherapy include:

  • Conformal radiotherapy (3D)
  • Intensity-modulated radiotherapy (IMRT)
  • Stereotactic radiotherapy

Conformal radiotherapy

This is also called 3D conformal radiotherapy. Here CT or MRI scans are used to make a three-dimensional (3-D) computer image of your tumour and nearby tissues. The radiotherapist puts metal blocks in the path of the radiation beam; the blocks change the shape of the beam so that it conforms more closely to the shape of the tumour. This allows a higher dose of radiation to be given to the cancer and a much smaller dose to normal tissue. This helps to reduce the risk of long-term side effects.

Intensity-modulated radiotherapy (IMRT)

With IMRT, your specialist can change the dose and match the shape of the rays to the shape of your tumour. The entire tumour gets the same dose of radiation, while healthy tissues close to the tumour receive a lower dose. This helps to prevent long-term side effects.

If you would like to know more about different types of radiotherapy, please see our section on advanced radiotherapy.

External radiotherapy treatment visits

Your first visit to the radiotherapy unit will be for planning purposes only. You will be asked to lie on a hard table and stay still for a few minutes while a machine called a simulator takes X-rays and scans of the area to be treated. This will help to plan the correct position for your radiotherapy.
Before treatment can begin, your skin will be marked to show where the treatment is to be aimed. This is done with ink or a permanent tattoo. The rays are then aimed at the same area each day. Do not rub off any marks made with ink until your treatments are over. This planning visit can take up to 45 minutes.

Treatment visits

You will visit the radiotherapy unit each weekday with a rest at weekends. This could last for up to 8 weeks. The radiotherapy machine moves around your body but does not touch you and makes very little noise. It is like having an X-ray and you will not feel anything during the treatment. You will be on your own in the treatment room but the radiation therapists will be able to see and hear you.

The treatment visits are much shorter than the planning visit. The treatment only lasts for about five minutes but your appointment will take about 15-20 minutes. This is because the radiation therapists will need time to put you in the right place on the treatment table.

Internal radiotherapy (brachytherapy)

Brachytherapy or ‘close dose’ therapy is a delivery system that provides high dose radiation to a small volume of tissue.
Internal radiotherapy is given in 2 main ways:

Putting radioactive seeds or rods inside your tumour (used in the treatment of prostate, cervical and endometrial cancer)

As radioisotopes to treat thyroid cancer. This will take the form of a drink or capsule or as an injection into a vein.

There are 2 types of brachytherapy, depending on the dosage:

  • Low-dose-rate (LDR) brachytherapy
  • High-dose-rate (HDR) brachytherapy

LDR brachytherapy

This involves putting radioactive seeds directly into your tumour and leaving them there permanently. In Ireland, LDR brachytherapy tends to be used for treating men with prostate cancer. Inserting the seeds requires a straightforward surgical procedure.

Before the procedure:
Your doctor may arrange some tests to check that your heart, lungs and kidneys are working well. Tell your doctor if you are taking any tablets to thin your blood, such as aspirin or Warfarin.

During the procedure:
You will not feel anything, as you will be put to sleep under general anaesthetic. The seeds will be put in using long needles and X-rays to guide the doctor. The number of seeds used depends on your type of tumour. The seeds are left in place and slowly release radiation over several months. The treatment is usually completed in a single visit.

After the procedure:
Once the procedure is finished, you will be taken to a room to recover until you are fully awake. You will usually be discharged from hospital the same day once you have had something to eat and drink.

Arrange for someone to bring you home. It is best not to drive for at least 12 hours afterwards. You will need to take antibiotics for a few days afterwards to prevent any infection. Before you leave, you will be given the contact details for the hospital and a follow-up appointment as well.

High dose rate (HDR) brachytherapy

This is used mainly to treat cancers in the head and neck area, the cervix, womb, prostate or the skin. High dose rate (HDR) brachytherapy involves a temporary implant of radioactive material (the source).

Tubes called applicators are put into your tumour under general anaesthetic so that the radioactive source can reach the tumour. The radioactive source stays close to or inside the tumour between 5 and 15 minutes, sometimes you may need a few treatments a week apart. In some hospitals the applicators are left in place between treatments. Once the treatment is over the tubes are removed.

Radioisotopes for thyroid cancer

For cancer of the thyroid, the radiation source may be unsealed or open. It involves using a liquid source of radiation called a radionuclide (radioisotope). It can be given as an injection into a vein but is more usually taken by mouth as a capsule. Unsealed sources are radioactive until your body gets rid of them.

Before treatment you will be brought to a special room with an en-suite. Here you will be asked to take a capsule of radioactive iodine. You will have to stay in this room for a number of days as your urine and stools will be radioactive. Usually after three days you will be allowed home. Your doctor, nurse or physicist will advise you on any precautions that need to be taken about this type of treatment.

How long do courses of radiotherapy last

How much treatment you receive will depend on the size, location and type of cancer. Your treatment will be planned to suit your situation. Even patients with the same type of cancer may have different radiotherapy treatments. Your doctor will discuss this with you.

With external radiotherapy, treatment can last from 4 to 8 weeks. With LDR brachytherapy, you will have one visit to put the seeds in and they stay in permanently. With HDR brachytherapy you may need only 1 treatment.

Is radiotherapy safe?

In general, radiotherapy is safe. Depending on the type of radiotherapy you receive, you may have to take some special precautions.

External radiotherapy

It is safe to be with other people, including children, throughout your treatment.

Low dose rate (LDR) brachytherapy

Although the seeds are radioactive, you are not. It is fine for you to be among people. But you do need to be careful around women who are pregnant and young children. It is fine for you to give them a quick hug or to be in the same room as them. But it is best not to allow children to sit on your lap or sit next to a pregnant woman for long periods of time for two months after treatment.

High dose rate (HDR) brachytherapy

You may have to stay in hospital for a few days. Certain safety measures will be taken to prevent exposing hospital staff and your friends and relatives to radiation. Once the treatment is over, there is no risk of harming your family or friends with radiation.


Special care will be taken after treatment with a liquid radioisotope.

  • You will most likely be in a side room, away from the main ward.
  • The doctors and staff on the ward will only stay in your room for short periods at a time.
  • Children and pregnant women will not be allowed to visit.
  • The level of radiation in your room will be monitored. The nurses may wear a small radiation counter.
  • Visitors may only be allowed to stay in the room or sit at the end of the bed for a very short time, if at all.
  • You will only be in the side room for a short time. You will be able to watch TV or listen to the radio and can bring books and magazines to read.

If you would like to know more about different types of radiotherapy, please see our section on advanced radiotherapy.

Side-effects of radiotherapy

For more information on the side-effects of radiotherapy please see our page on the side-effects of cancer treatments.

Contact our Cancer Nurseline

Freephone 1800 200 700 to talk to a specialist cancer nurse. It's open Monday-Thursday from 9am to 6pm and Friday from 9am to 5pm

By email:

Date Last Revised: 
Wednesday, March 2, 2016