Radiation therapy for breast cancer

Radiation therapy uses high-energy rays or particles to destroy cancer cells. It is often used to treat breast cancer. Your healthcare team will consider your personal needs to plan the type and amount of radiation, and when and how it is given. You may also receive other treatments.

Radiation therapy is given for different reasons. You may have radiation therapy to:

  • lower the risk of the cancer coming back, or recurring, after surgery (called adjuvant therapy)
  • shrink a tumour before surgery (called neoadjuvant therapy)
  • treat breast cancer that comes back, or recurs, in the area of a mastectomy
  • relieve pain or control the symptoms of advanced breast cancer (called palliative therapy)

Doctors use external beam radiation therapy to treat breast cancer. During external beam radiation therapy, a machine directs radiation through the skin to the tumour and some of the tissue around it.

Some women may not be able to have radiation therapy because they already had radiation therapy to the chest or breast. Doctors may not offer radiation therapy to women with lung problems, damaged heart muscles and certain connective tissue diseases.

Timing of radiation therapy

Radiation therapy is given once your breast heals after surgery. This usually takes 3 to 4 weeks. It can take longer if you get an infection or have problems healing. Research shows that radiation therapy may be given up to 8 to 12 weeks after surgery.

If chemotherapy and radiation therapy are both part of your treatment plan, radiation treatments are usually started after chemotherapy is finished. This is because the side effects of some drugs given for breast cancer may be worse if you also have radiation therapy.

Some treatment centres have waiting lists, and it can take some time for radiation therapy to begin. Try not to worry if you have to wait. Researchers have found that waiting up to 7 months to start radiation therapy after surgery (and after chemotherapy has already been given) doesn’t increase the risk that the cancer will come back in the breast tissue (called a local recurrence).

Radiation therapy after breast-conserving surgery

Radiation therapy is almost always given after breast-conserving surgery to lower the risk that cancer will come back in the breast. External beam radiation therapy is directed at all of the breast including the skin and the muscles on the chest. You may also be offered radiation to the lymph nodes under the arm (called the axillary lymph nodes) because research shows that this may lower the risk that the breast cancer will come back and may improve survival.

Sometimes doctors will give an extra dose, or boost, of radiation to the area from where the cancer was removed. They may give a boost if:

  • cancer cells are found in the tissue removed along with the tumour (called positive surgical margins)
  • the tumour is larger than 5 cm
  • the cancer is high grade
  • you are younger than 50 years of age

You may not need radiation therapy if all of the following apply:

  • you are 70 years of age or older
  • the tumour is 2 cm or smaller
  • the cancer has not spread to lymph nodes
  • the cancer cells are hormone receptor positive and you are taking hormonal therapy

Radiation therapy after a mastectomy

After a mastectomy, external beam radiation therapy may be directed to the area where the breast was removed, lymph nodes under the arm (called the axillary lymph nodes) and lymph nodes in front of the shoulder, near the collarbone.

Doctors may offer radiation therapy after a mastectomy if:

  • the cancer has spread to lymph nodes
  • the tumour was larger than 5 cm
  • the tumour grew into the skin or muscles

Radiation therapy is not usually given after a mastectomy if:

  • the tumour was smaller than 5 cm
  • the cancer has not spread to lymph nodes
  • cancer cells aren’t found in the tissue removed along with the tumour (called negative surgical margins)

Side effects

Side effects can happen with any type of treatment for breast cancer, but everyone’s experience is different. Some people have many side effects. Other people have few or none at all.

During radiation therapy, the healthcare team protects healthy cells in the treatment area as much as possible. But damage to healthy cells can happen and may cause side effects. If you develop side effects, they can happen any time during, immediately after or a few days or weeks after radiation therapy. Sometimes late side effects develop months or years after radiation therapy. Most side effects go away on their own or can be treated, but some side effects may last a long time or become permanent.

Side effects of radiation therapy will depend mainly on the size of the area being treated, the specific area being treated, the total dose of radiation and the treatment schedule. Certain medical conditions can make side effects from radiation worse.

Some common side effects of radiation therapy used for breast cancer are:

  • fatigue
  • skin problems
  • changes to the size and shape of the breast
  • changes to feeling in the breast
  • breast pain
  • lymphedema
  • difficulty moving the shoulder
  • heart damage
  • inflammation of the lung caused by radiation therapy to the chest (called radiation pneumonitis)

Tell your healthcare team if you have these side effects or others you think might be from radiation therapy. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them.

Questions to ask about radiation therapy

Find out more about radiation therapy and side effects of radiation therapy. To make the decisions that are right for you, ask your healthcare team questions about radiation therapy.

Expert review and references

  • American Cancer Society. Breast Cancer. 2015: https://www.cancer.org/.
  • Brackstone M, Fletcher GG, Dayes IS, Madarnas Y, SenGupta SK, Verma S, and Members of the Breast Cancer Disease Site Group . Locoregional therapy of locally advanced breast cancer: a clinical practice guideline. Current Oncology. 2015.
  • Morrow M, Burstein HJ, and Harris JR . Malignant tumors of the breast. DeVita VT Jr, Lawrence TS, & Rosenberg SA. Cancer: Principles and Practice of Oncology. 10th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2015: 79: 1117-1156.
  • National Cancer Institute. Breast Cancer Treatment for Health Professionals (PDQ®). 2015.
  • National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Breast Cancer (Version 2.2015). http://www.nccn.org/professionals/physician_gls/f_guidelines.asp.

Medical disclaimer

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