Radiotherapy for DCIS

Radiotherapy uses high-energy rays to destroy cancer cells, while doing as little harm as possible to normal cells. It is given after surgery to destroy any possible remaining cancer cells. You may be given it to reduce the risk of DCIS coming back or an invasive cancer developing. You usually start radiotherapy about four weeks after surgery.

After a wide local excision, your cancer specialist will recommend you have radiotherapy to the breast after your operation. Some women also have an extra dose to the area where the cancer was (a boost dose). Your cancer specialist may recommend radiotherapy if the DCIS is large or high-grade.

If you’ve been advised to have radiotherapy, your cancer specialist (clinical oncologist) will explain why it’s recommended for you. It’s important to talk about any concerns you may have with your specialist and your breast care nurse.

How it is given

You usually have radiotherapy for between three and five weeks. It’s given to you as an outpatient, so you come in for treatment and can then go home again afterwards. You have the treatment in the hospital radiotherapy department as a series of short daily sessions.

Each treatment session takes 10–15 minutes and they are usually given Monday–Friday, with a rest at the weekend. Your cancer specialist or nurse will talk to you about the treatment and possible side effects.

Radiotherapy doesn’t make you radioactive, and it’s safe for you to be with other people, including children, after treatment.

Planning radiotherapy

Radiotherapy has to be carefully planned to make sure it’s as effective as possible. It’s planned by a cancer specialist (oncologist) and it may take a few visits. On your first visit to the radiotherapy department, you’ll be asked to have a CT scan or lie under a machine called a simulator, which takes x-rays of the area to be treated.

You usually have markings made on your skin to show the exact place where the radiographers (who give you your treatment) direct the rays. Usually, permanent markings (tattoos) the size of a pinpoint are made. They’re only done with your permission. It can feel a little uncomfortable while they’re being made, but it makes sure treatment is given to the right area.

Radiotherapy is normally given to the whole breast. You may also be given an extra (boost) dose to the exact area where the DCIS was.

Treatment sessions

At the beginning of each session of radiotherapy, 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 will have to lie still for a few minutes during the treatment.


You’ll need to be able to position your arm so that the radiotherapy machine can give the treatment effectively. A physiotherapist can show you exercises to do to make this easier if your muscles and shoulder feel stiff or painful.

Back to Radiotherapy explained

Before your radiotherapy

Before you start radiotherapy, your team will explain what your treatment involves and how it may affect you.