MammoSite: An Internal Radiation Device for Breast Cancer Treatment

Most 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 two types of surgery for breast cancer:

• Breast conserving surgery also known as a lumpectomy , a wide excision, or a partial mastectomy . The surgeon removes the breast tumor and some normal tissue around it and attempts to conserve as much of the patient’s breast as possible.
• Total mastectomy , which is the 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 (external x-rays of the entire breast) 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 6-7 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 then 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.

MammoSite

The United States Food and Drug Administration (FDA) has approved a minimally invasive method of delivering internal radiation therapy following a lumpectomy. The device, called MammoSite, provides yet another alternative to traditional radiation therapy for women who have had a cancerous lump removed from their 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.

When used alone, treatment with MammoSite is usually administered twice a day for five days, greatly reducing the usual time required for radiation therapy.

Approved, but Still Experimental

The FDA found the MammoSite device to be equally as effective as other forms of brachytherapy currently being used to treat breast cancer. However, brachytherapy itself has not been found to be as effective as whole breast external radiation in preventing cancer recurrence. Therefore, brachytherapy of any kind for the treatment of breast cancer is still considered an experimental procedure. According to one expert, brachytherapy may offer real benefit to women who must be treated with radiation therapy following a lumpectomy. However, it will take time to see how it stacks up against whole breast radiation therapy as a means of preventing cancer recurrence on a long-term basis.

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.

Revision Information

• Reviewer: Igor Puzanov, MD
• Update Date: 03/29/2010