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Breast Cancer and Radiation Therapy—External

Written by sshowalter, FoundHealth.

External beam radiation therapy uses radiation produced by a machine called a linear accelerator. Short bursts of x-rays are fired from the machine at your cancer. The x-rays come out in square shapes. The radiation oncologist designs special blocks to shape the radiation beam so that it treats the cancer and as little normal tissue as possible.

Effect of Radiation Therapy—External on Breast Cancer

Radiation therapy can be given to treat cancer at its initial site or once it has spread. In some cases, once cancer has spread, radiation is no longer curative. However, the treatments can help resolve problems that the cancer may be causing, including pain and weakness.

Many people believe that once you have received a certain dose of radiation you can no longer get any more treatment. It is true that each tissue in the body can only safely tolerate a certain dose of radiation. However, the therapy is very focused and it is possible that you can get additional treatments to an already treated area, or certainly to an area not yet treated. Ask your radiation oncologist about what dose you can safely receive.

In most cases of breast cancer, radiation therapy is done after surgery. The standard treatment is after lumpectomy, when the remainder of the breast is still at risk for disease. But, if the tumor is large or any of the lymph nodes have cancer in them, your radiation oncologist will probably recommend you receive radiation therapy as well, even after a mastectomy.

In the US, if you need chemotherapy and radiation therapy, chemotherapy usually comes first. Unlike other cancers where both therapies are used, in breast cancer they are not offered at the same time because of an increased risk of side effects.

There are new developments in delivering radiation, including intensity modulated treatment (IMRT) and conformal therapy that allow finer control of dosage and treatment areas. These treatment types may be available in your area, and you may wish to discuss them with your doctor. Be aware, however, that such treatment is not needed in every case and that some highly respected scientists warn against it being used indiscriminately, resulting in increased costs for care with little improvement in outcome.

One new form of radiation delivered externally includes three dimensional conformal partial breast irradiation. This technique delivers twice daily radiotherapy to the area of the tumor plus a small margin. For women who are in the early stages of breast cancer, targeted external radiation may be delivered during surgery.


“Brachy” means “short,” and this form of treatment uses radiation therapy at very short distances. When you receive external beam radiotherapy, the radiation comes out of a machine located about 40 inches above you. Brachytherapy, however, delivers radiation directly to the cancer via a radioactive implant inside the body, usually by placing removable radioactive seeds within the surgical site.

Brachytherapy may be used to “boost” the dose delivered to the site of the cancer and spare the surrounding tissue from more radiation exposure. This special type of treatment is used at many centers in the US. Ask your radiation oncologist if it is appropriate for you. There are many methods to administer radiation therapy by means of brachytherapy to include the MammoSite balloon applicator and in-dwelling needle techniques. If you are a candidate for brachytherapy, your doctor will recommend one form or another based on the size and location of the tumor and her experience.

Read more details about Radiation Therapy—External.

Types of Professionals That Would Be Involved with This Treatment

The radiation oncologist will determine how many treatments you will receive. Each treatment generally only takes a few minutes, and the total treatment time can range from 5-8 weeks, depending on the total dose required.

Possible Complications

External radiation does not cause your body to become radioactive. It can cause side effects, as the radiation damages your own healthy cells as well as the cancer cells. Common side effects of radiation include, but are not limited, to:

  • Fatigue
  • Skin changes (redness, irritation)
  • Reduced white blood cell count
  • Hair loss
  • Nausea, vomiting, or diarrhea
  • Appetite loss

Discuss the specific side effects that you may have with your doctor.

Factors that may increase the risk of complications include:

  • Previous radiation therapy
  • A personal history of lupus , scleroderma , or dermatomyositis

A woman who is pregnant or could be pregnant should avoid exposure to radiation. It could harm a developing fetus.

Call Your Doctor

After arriving home, contact your doctor if any of the following occurs

  • Signs of infection, including fever and chills
  • Diarrhea or loss of appetite
  • Unexplained weight loss
  • Frequent urination, particularly if it is associated with pain or burning sensation
  • New or unusual swelling or lumps
  • Nausea and/or vomiting that you cannot control with the medicines you were given
  • Pain that does not go away
  • Unusual changes in skin, including bruises, rashes, discharge, or bleeding
  • Cough, shortness of breath, or chest pain
  • Any other symptom your nurse or doctor told you to look for
  • Any new symptoms

In case of an emergency, CALL 911.


American Lung Association website. Available at: . Accessed January 31, 2006.

Breast cancer. National Cancer Institute website. Available at: . Accessed January 27, 2006.

Detailed guide: breast cancer. American Cancer Society website. Available at: . Accessed January 27, 2006.

7/26/2010 DynaMed's Systematic Literature Surveillance : Vaidya JS, Joseph DJ, Tobias JS, et al. Targeted intraoperative radiotherapy versus whole breast radiotherapy for breast cancer (TARGIT-A trial): an international, prospective, randomised, non-inferiority phase 3 trial. Lancet. 2010;376(9735):91-102.

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