1. What is radiotherapy?
2. How is radiotherapy given?
3. Which areas are treated?
4. When will radiotherapy start?
5. Treatment planning
6. What happens during treatment?
7. Questions you may want to ask your specialist team
8. Getting to and from appointments
9. Radiotherapy side effects
10. Coping during treatment
11. After treatment finishes

1. What is radiotherapy?

The following information explains radiotherapy for people with primary breast cancer. If you have secondary breast cancer, you can read our information about treating secondary breast cancer.

Radiotherapy is a treatment for cancer that uses carefully measured and controlled high energy x-rays.

In primary breast cancer it aims to destroy any cancer cells that may be left behind in the breast area after surgery.

Radiotherapy has the greatest effect on cancer cells but also affects healthy tissue in the area being treated – however, this is generally able to recover and repair itself.

The total dose you receive is split into a course of smaller treatments (called fractions), usually given daily over a few weeks. The unit of dose is called a Gray or Gy for short. For example, a total of 40Gy may be given in 15 fractions over 15 working days (Monday to Friday).

Whether you’re offered radiotherapy will depend on your individual situation. It may not be possible to have radiotherapy if you have a medical condition that could make you particularly sensitive to the effects, or if you’re pregnant.

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

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2. How is radiotherapy given?

Radiotherapy is a specialised treatment and is not available in every hospital. However, each breast unit is linked to a hospital that has a radiotherapy department where you’ll be treated as an outpatient.

Radiotherapy is carried out by therapeutic radiographers (people trained to give radiotherapy). Most centres in the UK have male and female radiographers – if you would prefer to be treated by a female radiographer, talk to your oncologist, breast care nurse or therapeutic radiographer before or at your planning appointment.

External beam radiotherapy

External beam radiotherapy is the most common type of radiotherapy used to treat primary breast cancer. X-rays are delivered by a machine called a linear accelerator (linac) with the beam directed to the body through the skin.


Intensity modulated radiotherapy (IMRT)

Intensity modulated radiotherapy (IMRT) is another way of giving external beam radiotherapy.

With IMRT, the strength (intensity) of the radiation beam is varied (modulated), allowing different amounts of radiation to be given to different treatment areas. This enables healthy cells to be less exposed to radiation.

IMRT can be delivered by different types of machine - a standard radiotherapy machine (linac), a TomoTherapy machine with a built-in scanner, or a volumetric modulated arc radiotherapy machine (VMAT).

You can find out more about IMRT on the Cancer Research UK website.

The x-rays with external beam radiotherapy and IMRT do not make your body radioactive, so when you leave the treatment room you can safely mix with other people, including children.

Respiratory gating (breath hold technique)

Respiratory gating involves taking a deep breath in and holding it for a brief time. It’s done both at the treatment planning appointment and at each external beam radiotherapy treatment appointment. 

The purpose of respiratory gating is to help protect the heart from being affected by radiotherapy given to the left side. The heart is located on the left side of the body, and using a breath-hold technique can help protect the healthy tissues underneath the breast, reducing the chances of long-term side effects such as heart disease.

Your need for gating will be assessed and simple coaching instructions will help you maintain a suitable breath hold. Not everyone having their left side treated will need to use this method, and there are other ways to protect your heart that your specialist can talk to you about.

Other ways of giving radiotherapy

Advances in radiotherapy treatment for breast cancer are being made as a result of clinical trials, which look at different ways of giving treatment while minimising side effects. The following types of radiotherapy are less commonly used and are not widely available, but may be discussed with you.


Brachytherapy involves placing the 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. Then 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.

Intraoperative radiotherapy

Another method of giving internal radiotherapy is intraoperative radiotherapy. This is not yet widely used and isn’t suitable for everyone. Instead of using high energy x-rays directed from outside the body, this type of treatment uses low energy x-rays given from a machine in the operating theatre during breast-conserving surgery. Radiotherapy is given directly to the internal area 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.  

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3. Which areas are treated?

When deciding which areas to treat, your specialist team will consider factors such as the location, grade, size and stage of your cancer. You can find out more about how decisions are reached about your treatment by reading our pathology report web pages.

The breast 

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

The chest wall 

If you had a mastectomy (complete removal of the breast) for an invasive breast cancer, your specialist may recommend you have radiotherapy to the chest wall. This may be because:

  • the cancer was near the chest wall or deep within the breast tissue
  • there’s a high risk that cancer cells may have been left behind
  • cancer cells are found in the lymph nodes (glands) under the arm (axilla). 

Breast boost

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

Under the arm

Radiotherapy can also be given to the lymph nodes under the arm either instead of surgery or after a sentinel lymph node biopsy that shows there are cancer cells in the sentinel nodes. You can read more about assessing the lymph nodes on our surgery web pages.

The neck and collarbone

Your specialist may also recommend radiotherapy to the lymph nodes on the lower part of your neck, around your collarbone (called the supraclavicular fossa or SCF nodes), on the side you have had your surgery. This will depend on the grade and size of an invasive cancer, and whether the lymph nodes under the arm contained cancer cells. Your specialist will discuss this with you. 

The breast bone

Sometimes radiotherapy may also be given to the breast bone (sternum) to treat the lymph nodes in that area (known as internal mammary lymph nodes). If this is recommended, your specialist will explain why.

Radiotherapy and breast reconstruction

Many women consider having breast reconstruction after a mastectomy. This can be done at the same time as a mastectomy (immediate reconstruction) or at a later date (delayed reconstruction). Radiotherapy can affect the elasticity and quality of the skin over the area that is treated. For this reason, radiotherapy treatment may affect the timing and type of reconstruction suitable for each person. See our web pages about Breast reconstruction for more information.

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4. When will radiotherapy start?

Radiotherapy for primary breast cancer is given after surgery. If you’re having chemotherapy (treatment aimed at destroying cancer cells using anti-cancer drugs) after surgery, radiotherapy is usually given at the end of the chemotherapy. 

There are national guidelines in England that recommend you shouldn’t have to wait more than 31 days between surgery or the end of chemotherapy and the start of radiotherapy. However, it’s not unusual to wait a little longer than this. Radiotherapy can also be delayed for a medical reason, such as waiting for a surgical wound to heal. Elsewhere in the UK there are no guidelines for when radiotherapy should start after surgery or chemotherapy.

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

You’ll first see the specialist in the outpatient department to talk about your treatment. A further appointment is then made to plan your treatment. There may be some questions you want to ask your specialist team.

Guidelines for England and Wales recommend that the radiotherapy treatment is given every day over five days a week (Monday to Friday), for three weeks. However, depending on local guidelines and your personal situation your radiotherapy treatment may be given in a slightly different way, for example a smaller daily dose over a longer period of time. You’ll still be getting effective treatment. 

Where possible, your appointments will be arranged for a similar time each day so you can settle into a routine. It’s important that treatment continues as planned and that you don’t miss any appointments, as this can make the treatment less effective. 

Other drugs

It’s important to tell your specialist about any drugs you’re taking or considering taking. This includes vitamin and mineral supplements that are bought over the counter. Because of uncertainty about how safe it is to take vitamins, particularly high-dose antioxidants (including vitamins A, C and E, Co-enzyme Q10 and selenium), during your radiotherapy, many specialists recommend avoiding them. 

If you’re taking hormone therapy and having radiotherapy

In the past, there has been mixed evidence about whether it is better to start hormone therapy at the same time as radiotherapy, or after radiotherapy. However, recent evidence has shown that the order of treatments doesn’t matter. Your specialist will consider a number of things when deciding when to start hormone therapy, including other treatments you may have had or be having, and any ongoing side effects.

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5. Treatment planning

Precise treatment planning helps keep side effects from radiotherapy to a minimum, while accurately targeting the treatment area. Particular care is taken to try to avoid unnecessary radiotherapy to the tissues of the heart and lungs, and to avoid treating the same areas more than once when different angles are used to deliver the radiotherapy.

Treatment planning is necessary before your radiotherapy treatment to identify the exact area to be treated and the most effective dose of radiation. 

A number of people will be involved in planning your treatment, including:

  • your oncologist or a member of their team
  • a therapeutic radiographer
  • a radiation physicist (specialist in the measurement of radiation). 

They will look at your individual situation carefully before a specific treatment plan is worked out. 

Treatment planning is usually done using a CT (computerised tomography) scanner. A CT scanner takes x-ray images to produce a detailed 3D model of you. This means your team can plan the exact area to be treated while limiting the amount of radiation to surrounding tissues. This scan is only for planning your treatment, not for any other assessments.

Depending on the type of equipment used, the planning session will take between  15 minutes to an hour. You’ll need to lie very still while your arm on the side being treated is positioned above your head and supported in an arm rest. In some units you may be asked to raise both arms above your head, even though you’ll only be having treatment to the side where the cancer was.

It’s important that you’ve regained your arm movement after surgery and can comfortably raise your arm(s) above your head before you start, so treatment can be given to the whole breast or chest area. If this is difficult, talk to your breast care nurse or ask to see the physiotherapist, who’ll be able to advise you about arm exercises to improve the movement in your arm.

When the exact area of treatment has been decided, it’s important to have a record of the area to help position you precisely for each treatment. To do this, permanent ink markings (tattoos) are made on your skin to show where this is. It’s usually done by making very tiny permanent skin dots (usually three) using a pinprick of ink. If this is a concern for you, ask your therapeutic radiographer if any other options are available. 

Some women prefer to have their radiotherapy tattoos removed after finishing their treatment. You will need to check with your specialist as tattoo removal is not routinely available on the NHS and the results can vary.

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

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6. What happens during treatment?

When you go for treatment you’ll be asked to lie down on the treatment couch with your arm(s) above your head. If you’re wearing a gown, the therapeutic radiographer will adjust it to expose the area to be treated. They’ll help position you carefully, so that each time you have treatment you’re in exactly the same position you were during the treatment planning. 

You’ll be asked to stay very still during treatment, but you can breathe normally. If you’re having respiratory gating, your therapeutic radiographer will tell you how and when to hold your breath.

Treatment to the breast or chest wall is usually directed from different angles. The radiographer responsible for your treatment will reposition the machine for each angle. The machine may come quite close to you and even touch you. However, you won’t feel any sensation while the treatment is being given, although you may feel a little uncomfortable staying in the treatment position.

The treatment takes only a few minutes. Linear accelerators (linac) make a buzzing noise while in operation. Although you’ll be left alone in the room, the radiographers will watch through a window or on a television screen. Most radiotherapy departments also have an intercom system so that you and the radiographers can talk to each other.

If you’re going to have a boost, it will usually be given at the end of treatment, usually as five to eight extra sessions on a different type of machine.

If you’re having IMRT, the boost can be given by planning the radiotherapy to deliver a higher dose to this area during treatment.

The radiographers treating you will check how you are before each treatment. They can also answer your questions, give you advice on any side effects you may have and arrange an appointment with your specialist or breast care nurse if necessary. Alternatively, appointments to see one of your specialist team may be arranged during treatment so you can ask questions and discuss any concerns.

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7. Questions you may want to ask your specialist team

Here are some suggestions for questions you might want to ask your specialist team:

  • Why are you recommending radiotherapy for me?
  • What are the benefits and risks?
  • What are the side effects?
  • Are there any other treatments I could have?
  • Which area(s) will be treated?
  • How long will the radiotherapy take and how often will each treatment be given?
  • How long will I have to wait before starting treatment?
  • Will having radiotherapy affect my reconstructed breast or my options for breast reconstruction in the future?
  • What is my risk of lymphoedema (swelling of the arm, hand or breast/chest area)?
  • Are there any clinical trials for radiotherapy I could take part in?

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8. Getting to and from appointments

Most people feel able to drive themselves to and from their regular radiotherapy appointments. Whether you drive or use public transport, travelling to your treatment several times a week can be expensive, but help may be available. 

If you come by car, you may be able to have a special hospital pass which means you won’t have to pay car 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 or bus or train fares. Alternatively, there may be community transport services in your area or organisations with volunteer drivers who give people lifts to and from hospital.

Macmillan Cancer Support has information on benefits and financial support that outlines what you may be entitled to. The NHS leaflet Help with health costs (HC11) may also be useful.

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.

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9. Radiotherapy side effects

Everybody reacts differently to radiotherapy but certain side effects are more common than others. Although most side effects are temporary, some may be permanent and some may appear months or even years after treatment finishes.

Read more about side effects of radiotherapy.

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10. Coping during treatment

Being told you need radiotherapy can cause a range of emotions. Many people feel positive and secure knowing that everything possible is being done to treat their breast cancer. Some people feel upset, frightened or have difficulty adjusting to what’s happening to them and may be worried about their planned treatment. Fear of the unknown is common, so finding out as much as possible about your radiotherapy may help you cope better. 

Many centres have times when you can visit the radiotherapy department beforehand so you know what to expect. You can ask your breast care nurse about arranging a visit.

If you’re feeling low, tired or anxious at any point during or after your treatment, remember there are people who can help you. Tell your specialist or breast care nurse how you’re feeling so that they can offer help and support, and let family and friends know too.

You can also call the Breast Cancer Care Helpline on 0808 800 6000 for information and support.

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11. After treatment finishes

Once you’ve finished treatment it may take some time to get back to your everyday routine. Try not to expect too much of yourself in the early days and weeks after your treatment and give yourself time to heal and regain your strength. You may continue to feel tired for some time, but gradually you’ll start to feel better. For some people, this may take several months and sometimes longer.

For many people, radiotherapy is the last hospital-based treatment and the end goal they focus on, and getting there can feel like real progress. But some people also feel isolated, low and fearful, especially when their regular hospital appointments stop. If you feel like this you don’t have to cope alone. Our Moving Forward information and services can help. 

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Last reviewed: January 2017
Next planned review begins 2019

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