Side effects of radiotherapy

You may develop side effects over the course of your treatment. These usually disappear gradually over a few weeks or months after treatment finishes. Your doctor, nurse or radiographer will discuss this with you so you know what to expect. Let them know about any side effects you have during or after treatment. There are usually things that can be done to help.

Skin irritation

Your skin in the treated area may get red, dry and itchy. Dark skin may get darker or have a blue or black tinge. Your nurse or radiographer will give you advice on looking after your skin. If it becomes sore and flaky, your doctor can prescribe creams or dressings to help this.

Skin irritation usually goes away two to four weeks after radiotherapy.

Here are some tips to help:

  • Don’t put anything on your skin in the treated area without checking with your nurse or radiographer first.
  • Have a warm shower rather than a bath if you can. Turn away from the spray to protect your breast.
  • Gently pat the area dry with a soft towel. Don’t rub the area.
  • Wear loose clothing that is less likely to irritate your skin.

You need to avoid exposing the treated area to sunshine for at least a year after treatment finishes. Use suncream with a high sun protection factor (SPF) of at least 30 to protect your skin if it’s exposed.


This is a common side effect that may last for up to a month or two after treatment. Try to get plenty of rest and pace yourself. Balance this with some physical activity, such as short walks, which will give you more energy.

Aches and swelling

You may have a dull ache or shooting pains in the breast that last for a few seconds or minutes. Some women may also notice that their breast becomes swollen. These effects usually improve quickly after treatment. Some women still have occasional aches and pains in the breast area after radiotherapy.

Late effects of radiotherapy

Radiotherapy to the breast may cause side effects that happen months or years after radiotherapy. If you are worried about any side effects, talk to your cancer specialist.

The most common late effect is a change in how the breast looks and feels.

Small blood vessels in the skin can be damaged by radiotherapy. This can cause red ‘spidery’ marks (telangiectasia) to show.

After radiotherapy your breast may feel firmer, and shrink slightly in size. If your breast is noticeably smaller you can have surgery to reduce the size of your other breast. If you had breast reconstruction using an implant before radiotherapy, you may need to have the implant replaced.

Rarely, radiotherapy can cause heart or lung problems, or problems with the ribs in the treated area. Newer ways of giving radiotherapy help reduce the risk of these late effects.

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