Clinical experience with the MammoSite radiation therapy system for brachytherapy of breast cancer: results from an international phase II trial.

BACKGROUND AND PURPOSE

In a prospective multi-center phase II trial, we investigated the MammoSite Radiation Therapy System, a new device for delivering intracavitary brachytherapy following breast conserving surgery. The MammoSite is a dual lumen, closed ended catheter with a small, spherical inflatable balloon and a port for connecting a remote afterloader to the central lumen. We analyzed the surgical procedure and placement of the MammoSite, treatment planning and radiation delivery complications and cosmesis, as well the comfort for the patients.

PATIENTS AND METHODS

Between 2002 and 2004 a total of 32 patients (pts) were implanted using the MammoSite. The reference isodose was defined 1cm from the balloon surface. We analyzed the post-implant anatomic position of the applicator and the geometric form of the balloon via ultrasound, CT and X-ray, related side effects, cosmetic outcome and patient quality of life.

RESULTS

Twenty-three out of 32 patients (72%) were eligible for MammoSite intracavitary brachytherapy. Twenty-eight percentage had to be excluded because of different reasons. Eleven patients were treated with primary brachytherapy with a total dose of 34 Gy (2 x 3.4 Gy) and 12 had a boost with a mean dose of 13.3 Gy (range: 7.5-15 Gy; 2 x 2.5 Gy) combined with EBRT and doses ranged between 46 and 50 Gy. In three cases a balloon rupture occurred. We observed two abscesses within 3 months of implantation and serious seroma development in 10 patients (39%). Skin related side effects were erythema in 21 patients (91%), hyperpigmentation in 13 patients (56%) and teleangiectasia in six patients (26%) after mean follow-up 20 months.

CONCLUSIONS

The MammoSite Radiation Therapy System is a feasible treatment modality for intracavitary brachytherapy of breast cancer after breast conserving surgery. The advantage of the system is only one applicator is necessary for the delivery of a fractionated radiotherapy. In addition, patient tolerance of the procedure is high. Critical issues concern possible overdosages at the skin reflected by a high rate of late skin damage after only 20 months of follow-up time. The method could serve as an alternative to conventional multi-catheter brachytherapy for a selected group of patients.