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MammoSite: An Internal Radiation Device for Breast Cancer Treatment

woman talking to her doctorMost early stage breast cancers are treated, at least initially, with surgery. The main goal of breast cancer surgery is to completely remove the tumor from the breast. There are 2 types of surgery for breast cancer:

  • Breast-conserving surgery—Commonly known as a lumpectomy, or a wide excision or partial mastectomy. The surgeon removes the breast tumor and some normal tissue around it and attempts to conserve as much of the breast as possible.
  • Total mastectomy—Complete removal of the breast.

Traditional Radiation Therapy

Most women who are treated with breast-conserving surgery are also treated with radiation therapy. This is because undetectable microscopic cancer cells may be left behind after surgery. Radiation therapy is used in an attempt to destroy these remaining cancer cells and reduce the chance for the recurrence of the disease. Unfortunately, in addition to destroying cancer cells, traditional radiation therapy affects normal, healthy breast tissue as well. To help minimize this damage, radiation therapy is generally delivered in carefully measured doses over a period of several weeks.

Internal Radiation Therapy

An alternative to traditional radiation therapy is internal radiation therapy, also called brachytherapy. This type of radiation therapy allows the radiation source to be placed inside the breast as close as possible to the cancer cells. Radioactive material is placed directly into the site where the tumor was removed, allowing the radiation to concentrate on any remaining cancer cells while minimizing damage to the surrounding normal breast tissue. These implants are removed after a short period of time.


A device called MammoSite is one method that provides an alternative to traditional radiation therapy for women who have had a cancerous lump removed from her breast by lumpectomy.

The MammoSite radiation therapy system (RTS) is a single, small balloon catheter that fits inside the cavity left behind by the removal of the cancerous tumor. Then, a tiny, radioactive seed, which is connected to a machine called a high dose rate remote-afterloading device, is inserted into the balloon. It is this seed that delivers the radiation therapy, effectively focusing the highest levels of radiation directly on the area of the breast at the highest risk for cancer recurrence.

Which Option is Right for You?

Brachytherapy may offer real benefit to women who must be treated with radiation therapy following a lumpectomy. If you have been diagnosed with breast cancer, speak with your radiation oncologist to see whether you are a candidate for lumpectomy and whether brachytherapy may be an appropriate treatment choice for you.


American Cancer Society

National Cancer Institute


Canadian Breast Cancer Foundation

Canadian Cancer Society


Emerging areas in radiation therapy. The Susan G. Komen Breast Cancer Foundation website. Available at: Updated September 7, 2017. Accessed October 5, 2017.

MammoSite: FDA 501K summary. US Food and Drug Administration website. Available at: Published July 7, 2009. Accessed October 5, 2017.

Radiation therapy for breast cancer. EBSCO DynaMed Plus website. Available at: Updated December 22, 2015. Accessed October 5, 2017.

Vargo JA, Verma V, Kim H, et al. Extended (5-year) outcomes of accelerated partial breast irradiation using MammoSite balloon brachytherapy: patterns of failure, patient selection, and dosimetric correlates for late toxicity. Int J Radiat Oncol Biol Phys. 2014;88(2):285-291.

Last reviewed October 2017 by EBSCO Medical Review Board Michael Woods, MD, FAAP  Last Updated: 11/6/2015