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

Background and purposeIn 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 methodsBetween 2002 and 2004 a total of 32 patients (pts) were implanted using the MammoSite®. The reference isodose was defined 1 cm 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.ResultsTwenty-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 (2×3.4 Gy) and 12 had a boost with a mean dose of 13.3 Gy (range: 7.5–15 Gy; 2×2.5 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.ConclusionsThe 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.