Possible Side Effects

Side effects, if they do occur, are usually temporary and should subside shortly after treatment ends. Side effects are cumulative, which means they can develop over several weeks as the radiation accumulates in the tumor. You can ask your oncologist what you might expect from your specific treatment.

These are some common side effects of breast cancer radiation therapy:

  • Skin irritation similar to sunburn. Your healthcare team may advise you to avoid exposing the treated skin to the sun because it may worsen the skin condition.
  • Mild to moderate breast swelling during treatment. However, in some women, the breast becomes smaller and firmer after radiation therapy. Changes to the breast tissue and skin usually go away in six to 12 months.
  • Mild fatigue that generally improves a month or two after treatment ends.
  • A few women report mild tenderness in the breast or chest wall.
  • Internal scarring of a small part of the lung just under the breast.
  • Some patients experience swelling to the ipsilateral arm (the arm that's closest to the area being treated) that may result in a reduced range of motion.
  • Lymphedema (Swelling caused by an accumulation of lymphatic fluid).
  • Reduced blood count.
  • Fibrosis, or thickening/scarring of a small spot of tissue inside the breast.