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What are the side effects of radiation therapy for breast cancer?

Many patients with breast cancer will receive radiation therapy (sometimes referred to as radiotherapy) at some point in their treatment course. External beam radiation therapy (EBRT) delivers painless, high-energy particles to destroy or damage cancer cells. The radiation therapy precisely targets the breast and lymph nodes to stop the growth or spread of the breast cancer cells.

Some patients experience side effects from their treatment. Your treatment team will discuss these with you in more detail and a nurse will monitor any side effects regularly and assist you with management. If at any point you are worried about your treatment or side effects, do reach out to your doctor or nurse.

Common short-term, side effects of radiation therapy to the breast

  • Breast swelling
  • Skin changes in the treated area that are similar to a sunburn (for example, redness, skin peeling, and darkening of the skin, and occasionally blistering)
  • Changes in skin sensation 

If side effects do occur, your GenesisCare treatment team will monitor them closely. Side effects usually appear after the first two weeks of therapy, then may peak 5-10 days after treatment completes, and settle down thereafter. Most of these skin changes improve within a few months and usually go away within 6–12 months, but some women may experience skin effects for longer.

Other common short-term side effects include:

  • Fatigue, which varies in its severity between individuals and may persist for a few weeks after treatment has finished
  • Breast heaviness, tenderness, itchiness, and swelling (this may occur towards the end of treatment and can continue for a few weeks after radiation therapy has finished)

How can short-term side effects be managed?

To avoid irritating your skin, it is helpful to reduce the friction between the treated skin and clothing.

  • Wear loose, light clothing made of non-synthetic materials such as cotton
  • Avoid hot water and lotions that may irritate the treated area and use gentle soaps (non-perfumed and non-coloured soaps)
  • Avoid exposing the treated skin to the sun
  • Avoid exposing the area to direct heat (hair dryers, electric hot pads, hot water bottles)
  • Do not use adhesives or plasters on the treated area unless specifically recommended by your nurse or doctor. 

To manage fatigue, planning periods of rest throughout the day, as well as undertaking some gentle exercise (e.g. walking) and getting a good night’s sleep will all help. To ease any tenderness following treatment, your doctor may suggest taking mild pain relief.

Longer-term side effects of radiation therapy to the breast

Radiation therapy can cause side effects that emerge later in the treatment course or even after the treatment has been completed. You may experience some or none of these:

  • The breast may become firmer or change a little in size
  • Discolouration or tanning of the skin might occur and small red blood vessels (sometimes referred to as ‘spider veins’ may develop)
  • Lymphoedema or swelling in which fluid collects in the arm, breast, chest or back can develop when the lymph glands have been treated with surgery or radiation
  • In very rare cases, the ribs may be weakened leading to fracture
  • Problems with breastfeeding, including not being able to feed from the treated side but you may be able to feed from the other side. The treated breast will not swell up during pregnancy or when breastfeeding, so the size difference will be noticeable
  • Although rare, with modern radiation therapy equipment and techniques, long-term damage to the lungs and heart might occur
  • A very rare side effect is damage of the nerves to the arm (if the high lymph glands are treated), which can cause numbness, pain, and weakness of the shoulder, arm, or hand

Got questions or concerns?

It is normal to worry about possible side effects of your treatment. Your treatment team will discuss, assess and manage the side effects of your treatment. Your radiation oncologist and nurse will assess and monitor you for any side effects that you may experience both during or after treatment, and your treatment plan may be adjusted if needed. Remember, your nursing team and radiation oncology team are here to support you before, during and after your treatment.