Mammosite is a localized radiation treatment for breast cancer that is administered twice a day for five days. And it differs from typical external beam radiation therapy because instead of treating the entire breast, a radioactive seed is injected directly into the lumpectomy cavity to prevent the cancer from coming back.
According to Dr. David Hagan of Mid-Michigan Surgeons, "Most tumors where they recur in breast cancer, usually the recurrences are right on the edges of it. So this way you're treating the area where the tumor is most likely to recur rather than distant areas of the breast where it's less likely to show up."
Mammosite isn't recommended for everyone. Candidates include women over 40 years old, in an early stage of breast cancer with a tumor less than three centimeters in size.