Technology insight: MammoSite--a new device for delivering brachytherapy following breast-conserving therapy

The MammoSite (Cytyc Corporation, Marlborough, MA) breast brachytherapy applicator was designed to overcome the logistic problems created by external-beam radiation therapy (EBRT) and the technical difficulties associated with multicatheter-based interstitial brachytherapy. The MammoSite catheter has been shown to treat a volume of tissue equivalent to that treated by multicatheter-based brachytherapy. Using ultrasound guidance, the MammoSite applicator can be placed using an open technique at the time of lumpectomy or post-lumpectomy. Initial results have shown favorable cosmesis and few significant side effects. NSABP B-39/RTOG 0413 randomizes patients between EBRT and partial-breast irradiation (PBI). The PBI arm consists of interstitial brachytherapy, MammoSite brachytherapy, or 3D conformal EBRT. This trial has the potential to provide a definitive answer regarding the benefits of PBI for certain subgroups of patients, and hence lead to more women undergoing breast conservation therapy.