NEW ORLEANSTemplate-based interstitial brachytherapy is an effective
method for treating breast cancer, according to a study presented at the 44th
Annual Meeting of the American Society for Therapeutic Radiology and Oncology
(abstract 147). The study is one of the first to use a template to position
interstitial implants in its entire study population as part of its protocol.
"In properly selected patients, accelerated partial breast irradiation via
interstitial techniques offers 5-year results comparable to contemporary
standard breast conservation therapy with whole breast external beam
radiation therapy," said lead investigator Peter Y. Chen, MD, associate
director of education, Radiation Oncology, William Beaumont Hospital, Royal
Brachytherapy involves placing multiple catheters or needles into and
around the site of the lumpectomy. For low-dose-rate brachytherapy, a number
of radioactive sources are then manually afterloaded into the catheters. In
contrast, for high-dose rate brachy-therapy, one high-activity iridium-192
source is remotely afterloaded sequentially into each of the needles in a
specified amount of time at designated dwell positions to deliver precise
doses of radiation.
Conventional placement of the catheters or needles has been freehand
guided. A template allows exact geometric placement of the catheters/needles,
which improves the physician’s ability to target and control the delivery of
radiation to the tumor site. The template holds the breast physically in
place and, in conjunction with diagnostic imaging, provides a navigational
aid in placing the catheters/needles in the tumor bed. For women receiving
high-dose-rate outpatient therapy, the needles remain in place for the 4 to 5
days of twice-daily treatment.
In the study, 199 women with early-stage breast cancer were treated
according to one of three protocols of tumor bed irradiation alone:
low-dose-rate implant with I-125 as the radiation source treated continuously
as an inpatient (50 Gy over 96 hours) (n = 122) or high-dose-rate implant
with Ir-192 as the radiation source treated as an outpatient (32 Gy in eight
twice-daily fractions or 34 Gy in 10 twice-daily fractions) (n = 77). Every
implant was designed to irradiate the lumpectomy cavity plus a 1- to 2-cm
Patients ranged in age from 40 to 90 years (median, 65). Median follow-up
on all patients was 5 years (6.3 years for the low-dose-rate patients and 3.1
years for the high-dose-rate patients). A total of 129 patients (65%) have
been followed for 4 or more years, 95 (48%) for 5 or more years, and 70 (35%)
for 6 or more years.
The study originally included patients with up to three positive lymph
nodes, but was revised in 1997 to exclude patients with any positive nodes.
Other exclusion criteria included pure ductal carcinoma-in-situ, infiltrating
lobular histology, an extensive intraductal component, and significant
lobular carcinoma- in-situ, as well as breasts that were technically not
suitable for the implant.