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Breast cancer

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Radiation therapy for breast cancer

Radiation therapy uses high-energy rays or particles to destroy cancer cells. Radiation may be used for breast cancer:

  • after surgery or chemotherapy to destroy cancer cells left behind and to reduce the risk of the cancer recurring (adjuvantadjuvantTreatment given in addition to the first-line therapy (the first or standard treatment) to help reduce the risk of a disease (such as cancer) coming back (recurring). radiation therapy)
  • in combination with other therapies to treat stage III (locally advanced) breast cancer
  • to treat breast cancer that has recurred in the area of a mastectomy
  • to relieve pain or to control the symptoms of advanced breast cancer (palliative radiation therapy)

The amount of radiation given during treatment, and when and how it is given, will be different for each woman.

External beam radiation therapy

Breast cancer is usually treated with external beam radiation therapy. A machine directs radiation to the tumour and some of the surrounding tissue.

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After breast-conserving surgery

Radiation therapy is almost always given after breast-conserving surgery (BCS). Research has shown that radiation after BCS helps reduce the chance of cancer recurring in the breast. The entire breast, skin and chest wall are treated with radiation. The lymph nodes may or may not be treated.

Radiation therapy is usually given once a day, 5 days a week, for about 4–6 weeks after BCS.

  • The length of treatment may vary depending on the dose per treatment (called the fraction) and the total dose of radiation to be given.
  • In some treatment centres, radiation therapy may be given over a shorter period of time (such as 3 weeks).

Sometimes an extra dose (called a boost) is given to the area from where the cancer was removed to further reduce the chance of cancer recurring. A boost may be given:

  • if there are some cancer cells found in the area where the tumour was removed (positive or close margins) and more surgery is not possible
  • after radiation treatment to the breast when there is a high chance of local recurrence (cancer that comes back in the same area as the original tumour)
    • high grade, aggressive tumours
    • tumours larger than 5 cm in diameter
    • tumours close to the muscles of the chest wall

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After a mastectomy

After a mastectomy, external beam radiation therapy may be given to the chest wall and lymph nodes if there is a high chance of recurrence. Radiation therapy is usually given after mastectomy if:

  • There is cancer in many (4 or more) lymph nodes in the armpit.
  • The tumour is larger than 5 cm in diameter.
  • The tumour invades the chest wall or skin.

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Timing of radiation therapy

Radiation is given once the wound (incision) heals after breast cancer surgery, which usually takes about 3–4 weeks. The best period of time between surgery and starting radiation therapy is not really known, but in many treatment centres radiation therapy is started within 8–12 weeks after surgery.

In some situations, chemotherapy and radiation treatments may be given at the same time. More commonly, if chemotherapy and radiation therapy are both part of the treatment plan, radiation treatments are delayed until chemotherapy is finished. This is because the side effects of certain drugs may be worse when given in combination with radiation. These drugs include:

  • anthracycline drugs like doxorubicin (Adriamycin)
    • These drugs can also cause a skin reaction called radiation recall when given after radiation treatment.
  • taxanes like paclitaxel (Taxol)

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When radiation therapy is not used

Some women may not be able to have radiation therapy because of certain medical conditions or treatment history, including:

  • a disability or condition (such as arthritis) that prevents her from lying flat or stretching out her arm during radiation treatments
  • diseases that increase the risk of radiation therapy side effects
    • systemic lupus erythematosus – a connective tissue disease in which the immune system attacks the body’s own tissues and organs
    • scleroderma (thickening and hardening of the skin)
  • lung problems
    • reduced lung capacity
    • tuberculosis
  • damaged heart muscle (cardiomyopathy)
  • previous radiation therapy to the chest

See a list of questions to ask your doctor about radiation therapy.

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Dr Shawn Li I’m extremely grateful to the Canadian Cancer Society for funding my research with an Innovation Grant.

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