American Cancer Society answered:
Brachytherapy, also known as internal radiation, is another way to deliver radiation therapy. Instead of aiming radiation beams from outside the body, radioactive seeds or pellets are placed directly into the breast tissue next to the cancer. It is often used as a way to add an extra boost of radiation to the tumor site (along with external radiation to the whole breast), although it may also be used by itself (see below). Tumor size, location, and other factors may limit who can get brachytherapy.
There are different types of brachytherapy.
Intracavitary brachytherapy: This method of brachytherapy consists of a small balloon attached to a thin tube. The deflated balloon is inserted into the space left by the lumpectomy and is filled with a salt water solution. (This can be done at the time of lumpectomy or within several weeks afterward.) The balloon and tube are left in place throughout treatment (with the end of the tube sticking out of the breast). Twice a day a source of radioactivity is placed into the middle of the balloon through the tube and then removed. This is done for 5 days as an outpatient treatment. The balloon is then deflated and removed. This system goes by the brand name, Mammosite®. This type of brachytherapy can also be considered a form of accelerated breast irradiation. Like other forms of accelerated breast irradiation, there are no studies comparing outcomes with this type of radiation directly with standard external beam radiation. It is not known if the long-term outcomes will be as good.
Interstitial brachytherapy: In this approach, several small, hollow tubes called catheters are inserted into the breast around the area of the lumpectomy and are left in place for several days. Radioactive pellets are inserted into the catheters for short periods of time each day and then removed. This method of brachytherapy has been around longer (and has more evidence to support it), but it is not used as much anymore.
While these methods are sometimes used as ways to add a boost of radiation to the tumor site (along with external radiation to the whole breast), they are also being studied in clinical trials as the only source of radiation for women who have had a lumpectomy. In this sense they can also be considered forms of accelerated partial breast irradiation.Brachytherapy, also known as internal radiation, is another way to deliver radiation therapy. Instead of aiming radiation beams from outside the body, radioactive seeds or pellets are placed directly into the breast tissue next to the cancer. It is... More