Radiotherapy for breast cancer

You may be given radiotherapy to reduce the risk of breast cancer coming back in the breast, chest or lymph nodes.

Radiotherapy uses high-energy x-rays to destroy cancer cells. Normal cells can also be damaged by radiotherapy, which may cause side effects. But careful planning and newer ways of giving radiotherapy have reduced the risk of damage to healthy tissue and nearby organs. Cancer cells cannot repair themselves after radiotherapy, but normal cells usually can.

Radiotherapy after breast-conserving surgery

If you have breast-conserving surgery, your cancer specialist will recommend you have radiotherapy to the breast afterwards.

You usually start radiotherapy four weeks after surgery unless you are having chemotherapy. Radiotherapy is given after chemotherapy.

Radiotherapy after a mastectomy

Some women have radiotherapy after a mastectomy (removal of the breast). This depends on the risk of the cancer coming back in the chest area. Your cancer specialist may recommend radiotherapy after a mastectomy if:

  • the cancer was large
  • there were cancer cells in some lymph nodes in the armpit.

Radiotherapy to the lymph nodes

If the surgeon removed some lymph nodes from your armpit and they contained cancer, you may have radiotherapy to the rest of the nodes.

Some women also have radiotherapy to the lymph nodes above the collarbone and by the breastbone.

How radiotherapy is given

You usually have a course of radiotherapy for three weeks. Some women may need up to five weeks.

You have the treatment in the hospital radiotherapy department. Each treatment takes 10 to 15 minutes and they are usually given from Monday to Friday with a rest at the weekend. Women who have had breast conserving surgery also have an extra dose to the area where the cancer was (a booster dose).

Your cancer specialist or nurse will talk to you about the treatment and possible side effects.

Some women may have radiotherapy as part of a clinical trial.

External radiotherapy does not make you radioactive and it is safe for you to be with other people, including children, after your treatment.

Planning radiotherapy

Radiotherapy has to be carefully planned to make sure it works as well as possible.

It is planned by a cancer specialist (oncologist) and it may take a few visits. On your first visit to the radiotherapy department, you will be asked to have a planning CT scan. Or you may lie under a machine called a simulator, which takes x-rays of the area to be treated.

You will be given your treatment by radiographers. They make tiny permanent mark-ings (tattoos) the size of a pinpoint on your skin to show the exact place to aim the radiotherapy beams. It can feel a little uncomfortable at the time. This is only done with your permission.


The radiographer helps you put your arm into the best position for the radiotherapy to work. If your muscles and shoulder feel stiff or painful, a physiotherapist can show you exercises that can help.

Treatment sessions

At the beginning of each radiotherapy session, the radiographer will position you carefully on the couch and make sure you are comfortable.

During your treatment you’ll be alone in the room, but you can talk to the radiographer who will watch you from the next room.

Radiotherapy is not painful, but you have to lie still for a few minutes during treatment.

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