Radiation Oncology—High Dose Rate
Brachytherapy
St. Agnes Cancer Center now offers afterloading High
Dose Rate (HDR) Brachytherapy.
Brachytherapy is a form of radiotherapy whereby a radioactive
source is placed inside or alongside the target tissue (eg. tumor or area
where tumor was located prior to surgical removal) via a natural or created
channel. The radioactive source is introduced into the previously inserted
applicator (afterloading).
In HDR Brachytherapy, a high activity radiation source (12 Ci Iridium
source) is channeled through a single or multiple catheters. The administration
of radiaiton therapy is computer controlled. Each painless treatment session
lasts approximately 5-20 minutes. The patient only has radioactivity exposure
only during the treatment session. Patients who receive HDR Brachytherapy
may also receive external beam radiation, depending on the tumor site and
stage. HDR Brachytherapy is readily performed in an outpatient setting
with rare acute side effects. HDR Brachytherapy holds promise for more
aggressive which treatment by quickly delivering high radiation dosages
with excellent precision.
Remote afterloading has replaced the use of manual afterloading. To minimize
the radiation exposure of personnel, a computer controlled electro-mechanical
loading device for radioactive sources was developed. The Remote Afterloader
automatically places the radioactive source at predetermined positions
within the applicator and stores the source in between treatments. While
the patient is being treated, the personnel can stay ouside the room to
avoid radiation exposure.
For over ten years St Agnes has offered Low Dose Rate (LDR) Brachytherapy
which can be administered as permanent or temporary implants. This is most
commonly used in the treatmnent of prostate cancer with permanent radioactive
seeds implanted in the prostate and allowed to remain and deliver their
dosage over six to eight months. The seed placement is selected based on
a complex computer generated 3-dimensional treatment plan created intraoperatively
based on the patients prostate gland images seen on ultrasound.
Nationally, Prostate HDR Brachytherapy is increasing
in use for patients with patients who have carcinomas with more aggressive
features (Gleason score > 8). Similar to other HDR Brachytherapy treatments,
the radioactive source is only introduced to the prostate briefly and
avoids the lay concerns of radiation exposure associated with a permanent
seed implant.
The outpatient setting of HDR Brachytherapy can mean safer treatment for
some patients. Temporary LDR Brachytherapy has been used most commonly
for cervical carcinoma, endometrial carcinoma and sarcomas at the St Agnes
Cancer Center. Temporary LDR Brachytherapy typically requires a hospital
stay of two to four days with immobilization required. Deep venous thrombosis,
an uncommon risk of temporary LDR Brachytherapy due to the need for prolonged
immobilization, is avoided with HDR Brachytherapy.
St Agnes has partnered with Nucletron, inc., and has installed and already
treated several patients with the latest microSelectron HDR unit.
HDR Brachytherapy can be considered in the management
of the following malignancies:
- Breast—See separate article regarding Mammosite
Registry Trial
- Cervix—Used in combination with external beam
radiation therapy and chemotherapy.
- Endometrial—Used alone or in combination
with external beam radiation therapy as a treatment to the vaginal
apex postoperatively.
- Esophageal—Used palliatively to control
bleeding and obstruction.
- Head and Neck—Can be used for recurrence
in previously treated patients.
- Lung—Used for treating endobronchial
lesions and/or
hemoptysis.
- Pelvis—Sarcomas or Colorectal tumors where bowel
tolerance to external beam radiation therapy is dose limiting.
- Prostate—Emerging data supporting use as a boost to
external beam radiation therapy for patients with Gleason Score > 8.
- Sarcoma—Typically used
in combination with external beam radiation therapy for sarcomas
of the extremity.
- Skin—Conformal skin molds can be utilized.
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