Mammosite (www.mammosite.com) is the use of a high-dose-rate (HDR) brachytherapy source inserted into a specially-designed balloon catheter placed within the tumor cavity of breast cancer patients following breast conserving surgery.

Mammosite can be used to deliver a local boost following whole breast irradiation or definitively in patients treated with partial breast irradiation (PBI).

Initially developed in 2002, the Mammosite Radiation Therapy System (RTS) consists of a dual-channel catheter with a balloon on one end. One channel is used for the saline instillation (“black cap”), the other for the insertion of the HDR source (“red cap”).

Mammosite Radiation Therapy System (RTS)

The Mammosite catheter is placed in the lumpectomy either at the time of surgery or at a later date in a separate procedure.  The catheter exits through a separate skin incision or via the lumpectomy site.

The balloon is inflated with saline and a dilute contrast agent to variable sizes to accommodate the surgical cavity. The patient then undergoes a planning computed tomography (CT) Simulation to ensure that the breast tissues have conformed to the balloon’s outer wall and that there is an adequate balloon-to-skin distance.

After planning is complete, the catheter is attached to a HDR remote afterloader housing a high activity Iridium-192 source.

HDR Remote Afterloader

Under computer control, an HDR Iridium-192 source is inserted into the balloon via the catheter and left for a prescribed time interval (< 10 minutes).

The HDR source delivers a high dose to the nearby surrounding breast tissue.  Treatments are delivered twice daily over 5 days. A total dose of 34 Gy is prescribed.

If used solely as a boost only, a lower dose is delivered, typically over 1-2 days.

Schematic of the Mammosite Treatment

Once the treatment course is completed, the catheter is removed as an outpatient and the site is dressed. Treatment is typically well tolerated with little side effects during or following treatment.