Radiotherapy for primary breast cancer

Understand the ins and outs of radiotherapy, a treatment for cancer that uses carefully measured and controlled high energy x-rays. Learn more here.

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. 

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2. When radiotherapy is given

Radiotherapy is given after surgery to reduce the risk of breast cancer coming back.

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

If you don’t need chemotherapy, radiotherapy will usually start 4 to 8 weeks after surgery.

Your specialist or breast care nurse will explain when you will start radiotherapy.

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
  • You have been told you have an altered TP53 gene

3. Treatment areas

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 , you'll usually have radiotherapy to the remaining breast tissue on that side.

Your specialist may consider giving radiotherapy to the area of the breast where the cancer was removed, rather than the whole breast area. This is known as partial breast radiotherapy. It may be considered if the risk of the cancer coming back is low and you’re going to be taking for at least 5 years.

People with a very low risk of the cancer coming back may not need radiotherapy after breast-conserving surgery. Your specialist will discuss your risk and explain whether radiotherapy is needed.

After a mastectomy 

If you had a 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

If you’re 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 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. 

The total dose of radiotherapy is split into a course of smaller treatments. These are called fractions.

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 so you may have to travel for treatment.  

You’ll normally be given your treatment at hospital as an outpatient.

External beam radiotherapy (EBRT)

External beam radiotherapy (EBRT) is the most common type of radiotherapy used to treat primary breast cancer.

X-rays are delivered by a machine which directs beams of radiation at the area.

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

Intensity modulated radiotherapy (IMRT) 

Intensity modulated radiotherapy (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.

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 radiation beams. 

Other ways of giving radiotherapy 

The following types of radiotherapy are less commonly used and are not widely available, but may be discussed with you.

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 after it has been removed. Usually a single dose of radiation is given in one treatment. Sometimes you may also need 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.

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. The tubes or balloon are removed after your radiotherapy treatment is finished.

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. 

Brachytherapy is currently only given as part of a clinical trial. If brachytherapy is an option your specialist will discuss it with you.

5. How long will radiotherapy be given for?

Radiotherapy is usually given daily over 1 to 3 weeks. It will be given Monday to Friday with a break at weekends. Most hospitals do not give radiotherapy on bank holidays.

You may have radiotherapy for longer if you need an extra boost.

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.

Your specialist will explain how long you will have radiotherapy for and why.

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 so that together you can decide what arrangements to make.

It is important to attend all your radiotherapy appointments and avoid any gaps in the treatment as much as possible.

6. Before radiotherapy treatment

Your specialist will explain the details of the treatment, its benefits, risks and potential side effects. You will then be asked to sign a consent form.

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

If you'd prefer to have female radiographers during your radiotherapy treatment, talk to your treatment team during the planning appointment about this. It may not always be possible, but they will try their best to make sure you feel comfortable.

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. 

Treatment planning is usually done using a CT (computerised tomography) scanner.

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. You may be asked to hold your breath for a short period of time.

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

When the area of treatment has been decided, it’s important to 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. Some women prefer to have their radiotherapy tattoos removed after finishing their treatment. Tattoo removal is not routinely available on the NHS and the results can vary.

Newer techniques that don’t use tattoos to mark the area are being used in some hospitals. However, these are not widely available. Your specialist will discuss this if it is an option for you.

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. 

After surgery it can be difficult or painful to lift your arm above your head and keep it there. You will be given exercises to help regain arm and shoulder movement. If your arm movement isn’t improving you can talk to your breast care nurse or ask to see a physiotherapist. You can also take pain relief before each appointment to help you feel more comfortable holding the position.

7. During radiotherapy treatment

Once the planning and marking up is complete, your radiographer will arrange your first treatment appointment.

Getting into position 

You’ll be asked to undress above the waist and may be given a gown to wear. It can be helpful to wear a top that’s easy to take off and put on. You may be able to request female radiographers if you would prefer.

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 the same position.

Having radiotherapy

You’ll need to stay very still during treatment, but you can breathe normally unless you’re asked to do the breath hold technique, which is explained below. Treatment takes only a few minutes.

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 it’s on. The machine may come quite close to you and even touch you. However, you won’t feel the treatment being given. You may feel a little uncomfortable staying in the same position. 

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 and stop the treatment if needed.

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

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

Deep inspiration breath hold (DIBH) 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.

If you need to use breath hold you will be given simple coaching instructions and time to practise the technique. You can find video tutorials on how to prepare for using DIBH on the Respire website.

DIBH is done both at the treatment planning appointment and at each external beam radiotherapy appointment.

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 4 to 8 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 of radiotherapy

Like any treatment, radiotherapy can cause side effects.

Everyone reacts differently to treatment and some people have more side effects than others.

9. Other important information

Drugs and supplements

Tell your specialist about any medications you’re taking or considering taking. This includes vitamin and mineral supplements, herbal remedies and any treatments that are bought over the counter.

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

Because of this uncertainty, many specialists don’t recommend that people take high-dose antioxidant supplements during radiotherapy.

Transport and costs 

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

If you travel by car, you may be able to have a special hospital pass which means you won’t pay parking fees while having your radiotherapy.

If you claim benefits or are on a low income, you may be entitled to help with petrol costs, bus or train fares. There may be a hospital transport service, community transport services in your area or organisations with volunteer drivers who give people lifts to and from hospital.

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

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.  

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This information was published in October 2022. We will revise it in October 2024.

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