MammoSite Breast Brachytherapy

Radiation therapy is a common adjunct to cancer treatment (cancer removal) to make sure all the cancer cells have been destroyed. Radiation stops the cancer cells from repairing themselves and growing. MammoSite, also called balloon catheter radiation, is a form of brachytherapy (targeted radiation therapy), performed after the surgical removal of cancer tissue (lumpectomy) to destroy any residual cancer cells and prevent cancer from recurring.

The MammoSite system consists of a catheter (a thin tube) with a small, soft balloon at its tip to deliver high energy radiation beams. Appropriate for early stages of breast cancer, it targets a high-dose of radiation at the region where cancer recurrence is high. The course of treatment is typically twice a day for five days and each session takes about 30 minutes.


MammoSite therapy is recommended for the following:

  • Lumpectomy
  • Lymph nodes are negative for cancer
  • Age of 45 years and above
  • Small tumour (3 cm or less)
  • Should allow at least 7 mm of tissue between the skin and the inflated balloon
  • Cavity left behind after lumpectomy should be globular in shape to accommodate the inflated balloon


The MammoSite is an outpatient procedure and involves three processes: placement, treatment, and removal. Your surgeon makes a small incision in the breast and places the deflated balloon catheter inside the lumpectomy cavity (the empty space left when the tumor is removed). The balloon is then filled with saline so that it expands and fits correctly within the cavity. The filled balloon is left in place and stays inflated during the entire course of treatment. A small portion of the catheter is left outside the breast until the treatment is completed.  

During this treatment, the catheter is connected to a computer-controlled machine to insert a tiny source of radiation called a “seed” into the balloon that emits radiation. Once the treatment session is complete, the seed is withdrawn and the catheter is disconnected from the machine. Once your entire treatment course is completed, the saline is drained from the balloon, the balloon catheter is removed and the incision is closed with a bandage.

Post-procedure care

Care should be taken to keep the insertion site clean and dry.


You normally will feel no discomfort during or after the MammoSite treatment. However, you may sometimes experience minor breast-related side effects for a short period, including:

  • Redness or bruising at the catheter insertion site
  • Drainage
  • Breast pain
  • Infection


MammoSite radiation therapy is the most widely used method of accelerated partial breast irradiation due to the following benefits:

  • Reduced exposure of normal, healthy tissues and organs to radiation
  • Shorter duration of treatment, typically for 30 minutes, twice a day for five days, compared to the conventional radiation method that takes 6-7 weeks
  • Minimized side effects such as skin discoloration, burning, scarring and fatigue