NEW ORLEANSToxicity for low-dose-rate and high-dose-rate accelerated partial breast irradiation (APBI) (brachytherapy) is comparable to that observed in women treated with conventional whole breast external beam radiation therapy after lumpectomy, according to a 10-year study (RTOG 95-17) presented at the 44th Annual Meeting of the American Society for Therapeutic Radiology and Oncology (abstract 146).
"Acute toxicity with wide-volume brachytherapy was acceptable considering the learning curve that each institution had to go through, and should improve with newer catheter insertion techniques, including the use of templates," concluded Robert R. Kuske, Jr., MD, professor of human oncology, University of Wisconsin, Madison, and lead investigator of the study.
Dr. Kuske is the developer of the Kuske Breast Template (Nucletron Corporation, Columbia, Maryland), which recently received FDA approval for use in guiding catheter placement in breast brachytherapy (see photograph below).
The investigators enrolled a total of 100 women between August 1997 and March 2000 to receive high-dose-rate brachytherapy (34 Gy in 10 twice-daily fractions over 5 days) (n = 66) or low-dose-rate implants (45 Gy in 3.5 to 5 days) (n = 33). Patients had invasive nonlobular breast carcinomas of 3 cm or less with negative surgical margins after lumpec-tomy and axillary dissection with 0 to 3 positive axillary nodes without extracapsular extensions. One patient was excluded for having only sentinel node mapping.
Wide-volume brachytherapy involves placing multiple catheters or needles 2 cm around the lumpectomy site to deliver precise doses of radiation "from the inside out," Dr. Kuske said. Conventional placement of the catheters has been freehand guided. The Kuske Breast Template holds the breast in place and provides a navigational aid for image-guided catheter placement. The catheters remain in place for the 4 to 5 days of twice-daily outpatient treatment.
In the current study, catheter insertion procedures were left to the discretion of each individual institution, Dr. Kuske said, and data were not collected concerning individual freehand and template techniques used to accomplish volume coverage.