1. What is radiotherapy? 
2. When radiotherapy is given
3. Which areas are treated? 
4. How radiotherapy is given 
5. How long will radiotherapy last?
6. Before treatment starts 
7. During treatment 
8. Side effects 
9. Things to be aware of during treatment

1. What is radiotherapy? 

Radiotherapy uses high-energy x-rays to destroy cancer cells.

It’s given to destroy any cancer cells that may have been left in the breast and surrounding area after surgery. You may hear this called adjuvant radiotherapy. 

Radiotherapy is given using specialist machines.

You can also download a simple summary to find out more about radiotherapy for primary breast cancer.

2. When radiotherapy is given

Radiotherapy is given after surgery to reduce the risk of breast cancer coming back in the breast, chest area or lymph nodes.  

Your specialist or breast care nurse will tell you when you can expect to start radiotherapy. 

If you’re having chemotherapy after surgery, radiotherapy is usually given after the chemotherapy.

Radiotherapy may be delayed for a medical reason, for example if you need to wait for a wound to heal or if you develop a seroma (a collection of fluid that sometimes forms under a wound after an operation). 

Radiotherapy may not be suitable if:

  • you have previously had radiotherapy to the same area
  • you have a medical condition that could make you particularly sensitive to its effects
  • you’re pregnant

3. Which areas are treated?

When deciding which areas to treat and how, your treatment team will consider factors such as the location, grade, size and stage of your cancer. 

After breast-conserving surgery 

If you had breast-conserving surgery (a wide local excision or lumpectomy) you will usually have radiotherapy to the remaining breast tissue on that side.

Radiotherapy is usually given to the whole breast. 

Your specialist may consider giving radiotherapy to the area of the breast where the cancer was removed if the risk of the cancer coming back is low and you’re going to be taking hormone therapy for at least five years. This is known as partial breast radiotherapy. 

After a mastectomy 

If you had a mastectomy for an invasive breast cancer, your specialist may recommend you have radiotherapy to the chest wall. 

This may be the case if: 

  • the cancer was large or near the chest wall 
  • there’s a high risk that cancer cells may have been left behind after surgery 
  • cancer is found in the lymph nodes under the arm 
  • you have a type of cancer called inflammatory breast cancer

If you’re going to be having breast reconstruction, radiotherapy may affect the timing and type of reconstruction. 

Radiotherapy to the lymph nodes

Radiotherapy can be given to the lymph nodes under the arm to destroy any cancer cells that may be present there.

It may also be given to the lymph nodes in the lower part of the neck around the collarbone, or in the area near the breastbone (sternum).

If radiotherapy to the lymph nodes is recommended, your specialist will explain why.

4. How radiotherapy is given 

Radiotherapy can be given in several ways and using different doses, depending on your treatment plan. 

The total dose is split into a course of smaller treatments (called fractions), usually given daily over a few weeks. 

It’s carried out by people trained to give radiotherapy, known as therapeutic radiographers. 

Radiotherapy is not available in every hospital, but each breast unit is linked to a hospital that has a radiotherapy department. 

External beam radiotherapy 

This is the most common type of radiotherapy used to treat primary breast cancer. 

X-rays are delivered by a machine which directs a beam of radiation at the breast.

The x-rays do not make you radioactive, so when you leave the treatment room you can safely mix with other people, including children.

Intensity modulated radiotherapy (IMRT) 

IMRT is another way of giving external beam radiotherapy. 

The dose (intensity) of radiotherapy can be varied (modulated), allowing different amounts of radiation to be given to different areas. The risk of side effects is lower with IMRT because healthy tissue in the area gets a lower dose of radiation. 

IMRT is not available in all radiotherapy treatment centres.

Volumetric modulated arc therapy (VMAT)

This is a type of IMRT. The radiotherapy machine rotates round the area being treated, continuously changing the shape and intensity of the radiation beam. 

Other ways of giving radiotherapy 

Intraoperative radiotherapy 

Intraoperative radiotherapy uses low-energy x-rays given from a machine in the operating theatre during breast-conserving surgery. 

Radiotherapy is given directly to the area inside the body where the cancer was, once it has been removed. Usually a single dose of radiation is given in one treatment, but it may be necessary to have a short course of external beam radiotherapy to the rest of the breast. 

Intraoperative radiotherapy is not suitable for everyone and is not standard treatment. 


Brachytherapy involves placing a radiation source inside the body in the area to be treated. It’s usually only given as part of a clinical trial. 

Narrow, hollow tubes or a small balloon are put in the body where the breast tissue has been removed. Radioactive wires are inserted through the tubes or into the balloon. The radioactive wires may be left in place for a few days or inserted for a short time each day. 

Depending on the type of brachytherapy you have, you may need to have your treatment as an inpatient and be kept in a single room for a short time due to the radiation. 

If brachytherapy is an option your specialist will discuss it fully with you.  

5. How long will radiotherapy last? 

Radiotherapy is usually given for a total of three weeks. 

Treatment is given every day from Monday to Friday, with a break at the weekend. If there’s a bank holiday during this time, you’ll usually be given an extra session at the end to make up for the one missed.

Depending on local guidelines and your personal situation, your radiotherapy may be given in a slightly different way. For example, you may have a smaller daily dose over a longer period of time. Alternatively, your treatment team may recommend five daily treatments over one week (Monday-Friday).

For several years, clinical trials have been looking at giving radiotherapy over shorter periods. One large trial has recently confirmed that people who received the shorter regime (five daily treatments of radiotherapy in a week compared to fifteen daily treatments over three weeks) have similar results. The trial found that giving radiotherapy over the shorter time period was as safe and as effective as the longer period. The trial results so far are based on people who were followed up for five years in the two groups. The results following people up for ten years are to be published shortly.  

Based on these trials, radiotherapy experts believe shortening some people’s treatment is an acceptable way to be treated.

Your appointments may be arranged for a similar time each day so you can settle into a routine but this isn’t always possible.  

If you have a holiday booked, tell your specialist or therapeutic radiographer before or at your planning appointment so together you can decide what arrangements to make.

6. Before treatment starts 

You’ll first see your specialist to talk about your treatment. 

Once details of the treatment, its benefits, risks and potential side effects have been explained, you’ll be asked to sign a consent form. 

An appointment is then made to plan your treatment. 

When you have your first appointment with the specialist you may be asked to take part in a clinical trial

Treatment planning 

Treatment planning helps identify the exact area to be treated and the most effective dose of radiation, while limiting the amount of radiation to surrounding tissues. 

A number of people will be involved in planning your treatment. 

Treatment planning is usually done using a CT (computerised tomography) scanner. A CT scanner takes x-ray images which help your team plan the exact area to be treated. 

The planning session will take between about 15 minutes and an hour. 

You’ll need to lie very still while your arms are positioned above your head and supported in an arm rest. You may be asked to raise only the arm on the side being treated.  

Tell your specialist or therapeutic radiographer before or during your planning appointment if:

  • you have a pacemaker or implantable cardioverter defibrillator (ICD)
  • you think you might be pregnant

Marking the area

It’s important to have a record of the exact area of treatment. This will help position you precisely for each treatment. 

To do this, permanent ink markings (tattoos) are made on your skin. It’s usually done by making three tiny dots using a pinprick of ink. 

If you’re concerned about this, ask your therapeutic radiographer if any other options are available. 

Some women have their radiotherapy tattoos removed after finishing their treatment. However, tattoo removal is not routinely available on the NHS and the results can vary.

Regaining arm movement

It’s important that you have regained your arm movement after surgery and can comfortably raise your arm above your head before you start radiotherapy. This is so treatment can be given to the whole breast or chest area. 

If you find it difficult or painful to lift your arm above your head and keep it there, talk to your breast care nurse or ask to see the physiotherapist. They can advise you about exercises to improve the movement in your arm

You could also try taking some pain relief before each appointment to help you feel more comfortable holding the position. 

7. During treatment

Once planning and marking up are complete, your radiographer will arrange with you when to come for your first treatment.

Getting into position 

You’ll be asked to undress above the waist and you’ll be given a gown to wear. It can help to wear a top that’s easy to take off and put on. 

You’ll lie down on the treatment couch with your arms or arm above your head. 

The therapeutic radiographer will adjust the gown to expose the area to be treated. They’ll help position you carefully, so each time you have treatment you’re in exactly the same position you were during the treatment planning.



Having radiotherapy

You’ll need to stay very still during treatment, but you can breathe normally.

Radiotherapy to the breast or chest wall is usually given from a number of different angles. The radiographer will reposition the machine for each angle. 

The radiotherapy machine makes a buzzing noise while in operation. The machine may come close to you and even touch you. However, you won’t feel the treatment being given, although you may feel a little uncomfortable staying in position. 

Treatment takes only a few minutes. 

Although you’ll be left alone in the room, cameras will allow the radiographers to watch you on a television screen. Most radiotherapy departments also have an intercom system so that you and the radiographers can talk to each other.

The radiographers treating you will check how you are before each treatment. They can also answer any questions you have, give you advice on side effects and arrange an appointment with your specialist or breast care nurse if necessary. 

Alternatively, appointments to see a member of your treatment team may be arranged during treatment so you can ask questions and discuss any concerns.

Breath hold technique

This can help protect the heart from being affected by radiotherapy given to the left side.

It involves taking a deep breath in and holding it for a short time. Your therapeutic radiographer will tell you how and when to hold your breath. 

It’s done both at the treatment planning appointment and at each external beam radiotherapy appointment. 

Your need for breath hold will be assessed and simple coaching instructions will help you maintain a suitable breath hold. 

Not everyone having their left side treated will need or be able to use this method, and there are other ways to protect your heart that your specialist can talk to you about. 

Breast boost 

Your specialist may recommend a boost of radiotherapy to an area where invasive breast cancer was removed following radiotherapy to the whole breast. 

A breast boost is given at the end of treatment, usually as five to eight extra sessions. 

If you’re having IMRT, the boost can be given by planning the radiotherapy to deliver a higher dose to this area at the same time that the breast is being treated.

8. Side effects

Radiotherapy causes side effects because it affects healthy tissue as well as cancer cells. 

Find out about the side effects of radiotherapy.

9. Things to be aware of during treatment

Drugs and supplements

If you’re going to be taking hormone therapy, some specialists may suggest waiting until the radiotherapy is finished. This is so you don’t have to deal with side effects from two treatments at the same time. 

Tell your specialist about any drugs you’re taking or considering taking, including:

  • vitamin and mineral supplements
  • herbal remedies
  • any treatments that are bought over the counter 

The evidence isn’t clear whether supplements such as vitamins, particularly high-dose antioxidants (including vitamins A, C and E, co-enzyme Q10 and selenium), are harmful or helpful during radiotherapy. 

Because of this uncertainty, many specialists recommend people avoid taking high-dose antioxidant supplements during radiotherapy.

Transport and costs 

Most people feel able to drive to and from their radiotherapy appointments. 

Whether you drive or use public transport, travelling to and from your treatment or paying for parking can be expensive. 

However, help may be available.

You can find out about help with transport and parking on the Macmillan Cancer Support website. 

The NHS website also has information about help with health costs.  

If you think going to appointments will be difficult because of the cost or other travel issues, talk to your radiographer or breast care nurse to find out what help might be available. 

If you have a local cancer information centre, they may be able to tell you if any financial help or voluntary community transport is available in your area.

Last reviewed: May 2019, revised June 2020
Next planned review begins 2021

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