MammoSite System Seems Just as Good as Whole Breast Radiation

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Women who got internal partial-breast irradiation with the MammoSite system, also known as brachytherapy, had the same outcomes as women who got traditional external radiation therapy in the 3 to 4 years after lumpectomy to treat early-stage breast cancer.

The results were presented at the 2008 American Society for Therapeutic Radiology and Oncology (ASTRO) meeting.

Radiation therapy is used after lumpectomy to destroy any cancer cells that may be left behind and to reduce the risk of the cancer coming back. There are two main types of radiation.

External radiation, sometimes called external beam radiation, is the most common type of radiation. In this technique, a large machine called a linear accelerator aims a beam of high-energy radiation at the area affected by the cancer. This form of radiation is given on an outpatient basis 5 days a week, over 5 to 7 weeks, depending on the particular situation.

Internal radiation, or brachytherapy, typically uses small pieces of radioactive material, called seeds, which are placed in the area around where the cancer was. The seeds emit radiation into the surrounding tissue. The area that's very close to the site of the original cancer is the area that is at highest risk of recurrence. Internal radiation is most commonly delivered using multiple small tubes or catheters, or using a balloon-catheter device called MammoSite. Brachytherapy usually is given over 5 to 7 days, a much shorter time than external radiation. Still, brachytherapy systems require a skilled and experienced medical team and available radioactive materials.

In the MammoSite system, a catheter with a balloon on the end is placed in the area where the lumpectomy was done. The balloon-catheter device can be placed during lumpectomy surgery or in a surgeon's office soon after the lumpectomy. The end of the catheter pokes out through a small hole in the skin. The balloon is filled with fluid to hold the device snugly in place.

MammoSite brachytherapy radiation is usually given two times per day for 5 days. The women in this study followed this schedule. During each treatment, a machine places a radioactive seed into center of the balloon for up to 10 minutes. The seed is then removed. Women receiving brachytherapy can leave the treatment center between treatments -- they're not radioactive after the seed is removed. When the final treatment is done, the balloon is drained and removed through the hole in the skin.

More than 1,400 women who got MammoSite radiation from 2002 to 2004 were followed in this study. The results:

  • Within 3 years of initial diagnosis, 28 women (2%) had the breast cancer come back in the spot where radiation was given. This risk of recurrence was the same for women who got traditional external beam radiation.
  • Some of the women had breast cancer come back in places that the radiation therapy would have no effect on:
    • 3 women had the cancer come back in the underarm (axillary) area near the breast that had lumpectomy
    • 11 women developed a new breast cancer in the opposite breast
    • 16 women had the cancer come back in another part of the body

After 4 years, more than 94% of the women were alive and almost 90% were alive without the cancer coming back or being diagnosed with a new breast cancer.

More research with longer follow-up time will help doctors better understand which women will benefit the most from the MammoSite system. Some women may choose to have mastectomy instead of lumpectomy because it's too hard for them to get 5 to 7 weeks of daily radiation therapy after surgery. MammoSite and other brachytherapy systems can deliver radiation therapy in only 5 days. This may allow more women to choose lumpectomy over mastectomy.

If radiation therapy will be part of your treatment plan after surgery, you and your doctor will talk about which surgery and which radiation therapy technique makes the most sense for you. For some women, external radiation is the best approach. For others, internal partial-breast radiation therapy may be a good option. The Breastcancer.org Radiation Therapy section offers more information, including how radiation works to treat breast cancer, the different approaches to delivering radiation, and what to expect during and after treatment.

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