Brachytherapy for Breast Cancer
Breast conservation therapy (BCT) is a multi-modality alternative to mastectomy for treatment of early stage I or stage II breast cancer. Currently, most conventional BCT includes breast-conserving surgical excision of the tumor and whole breast radiotherapy delivered using external beam radiation. In addition, “boost” radiotherapy may be performed using brachytherapy; the interstitial or intracavitary implantation of radioactive material directly into the breast to target the segment of the breast surrounding the area where the tumor was removed.. Brachytherapy may also be given as the sole form of radiotherapy after surgical incision.

Various interstitial brachytherapy techniques have been investigated. They differ in the timing of implantation relative to other components of breast-conserving therapy, the radiation dose rate, the loading technique, the number and volumetric distribution of radioactive sources, and the radioisotopes used. Most of the older studies of local boost brachytherapy temporarily implanted needles, wires, or seeds after patients recovered from surgery and completed whole-breast radiation therapy. Since the 1990s, investigators have perioperatively implanted hollow needles or catheters that guide placement of the radioactive material. This can be done during the initial lumpectomy if brachytherapy has been selected already or at re-excision if the lumpectomy specimen has positive surgical margins. Intraoperative implantation avoids the need for a separate surgical procedure with anesthesia for brachytherapy.

Both low- and high-dose rate interstitial techniques are used, with high-dose rate techniques increasing in popularity. In the low-dose rate technique, radioactive seeds are temporarily implanted in hospitalized individuals. They deliver radiation continuously over 4 days and then are removed. In the high-dose rate technique, a computer-controlled device loads highly radioactive isotope sources into catheters that have been placed into the tumor bed. The individual is exposed to the radiation therapy for a brief period (e.g., 15 minutes) and then the radioactive sources are withdrawn. High-dose rate brachytherapy is typically administered to individuals on an outpatient basis as 8 fractions given twice daily over 4 days.