Brachytherapy is a type of treatment using sealed radiation sources to deliver a dose of radiation at a short distance, usually to an area or volume that is within 6 inches of the radiation sources. “Brachys” is Greek for “near”, thus, the radioactive sources are placed strategically within the tumor tissue (interstitial), inside a diseased cavity (intracavitary) or even on the surface of the disease site. With brachytherapy, a high dose of radiation is delivered to the tumor while the dose levels decrease rapidly in the adjacent healthy tissue. Clinical experience and studies have shown that tumor tissue response may depend on the rate at which the dose of radiation is delivered. Based on this need for tumor/site specific dose delivery, brachytherapy treatments may be divided into High Dose Rate (HDR) or Low Dose Rate (LDR) techniques.
A. High Dose Rate (HDR) Brachytherapy
During High Dose Rate (HDR) procedures, the radioactive source (Iridium 192) housed within the HDR unit is temporarily placed (on the order of minutes) adjacent to or within the tumor. With HDR techniques, the radiation oncologist can vary the radiation dosage with source placement resulting in more precise treatment doses and while minimizing the dose to healthy tissue in the immediate vicinity. At University Hospitals Seidman Cancer Center, the HDR brachytherapy service is treating patients with gynecologic, endobronchial, breast, and head and neck cancers.
B. Low Dose Rate (LDR) Brachytherapy
Low Dose Rate (LDR) Brachytherapy procedures rely on the surgical placement of sealed sources of radiation directly in or near the area being treated. LDR treatments are customized to the patient by varying the radiation source strength and placement and can be temporary (on the order of hours or days) or permanent. The University Hospitals Seidman Cancer Center LDR Brachytherapy service provides treatment to the following sites, the prostate gland, cervix, and eye.
Specific Treatments:
1) Permanent Prostate Seed Implant (PSI)
For this implant, small radioactive seeds (usually Iodine-125 or Palladium-103) are inserted into the prostate gland with the patient under general anesthesia.
In the operating room, images of the patient’s prostate are captured using ultrasound. The treatment planning computer software uses these ultrasound images to plan the seed distribution required to effectively treat the prostate. A computer printout, or template, is generated which indicates the seed placement coordinates and the radioactive seeds are placed using an ultrasound-guided needle. After the procedure is completed, the patient goes home (same day procedure).
The sources remain in tissue permanently and continue to decay delivering the radiation over a period of time, about 1 year for Iodine-125 and 3 months for Palladium-103.
2) Cervical Cancer using Tandem-Ovoids or Syed Template
Intracavitary gynecologic cancers, usually within the cervix, are treated using a temporary implant. Cesium-137 or Iridium-192 sources are inserted into the treatment site using a variety of applicators, such as Tandem-Ovoids and a Syed Template. The surgically placed sources remain at the treatment site between 1-5 days and the patients remain in the hospital for the duration of the treatment.
3) Eye Plaque
Eye plaque radiation treatment is offered for choroidal melanoma in adults. This treatment requires radioactive seeds to be placed in a plaque that will be sutured in place directly over the lesion in the operating room. The sources imbedded in the plaque direct therapeutic radiation toward the tumor while shielding the orbit and other surrounding anatomy. The plaque is then removed in the operating. The patient remains in the hospital for approximately 4 days for this treatment.