Permanent radioactive seed implants are a form of radiation
therapy for prostate cancer. The terms "brachytherapy" or "internal radiation
therapy" might also be used to describe this procedure.
During the procedure, radioactive (iodine-125 or I-125) seeds
are implanted into the prostate gland using ultrasound guidance. The number of
seeds and where they are placed is determined by a computer-generated treatment
plan tailored for each patient. About 100 seeds are commonly implanted.
The implants remain in place permanently, and become
biologically inert after about 10 months. This technique allows a high dose of
radiation to be delivered to the prostate with limited damage to surrounding
Compared to external radiation, which requires 7 to 7 ½ weeks of
daily treatments, convenience is a major advantage of this treatment option.
Who is eligible for this procedure?
Permanent implants are relatively low-energy sources, and therefore have
limited tissue penetration. A well-done implant will treat the prostate and the
surrounding 5 millimeters of adjacent tissue.
Therefore, the best candidates for this procedure are patients
who have a cancer that is contained within the prostate and is not very
aggressive. The usual criteria for treatment include a PSA level of less than
10, a Gleason score (which measures the aggressiveness of the tumor) less than
or equal to six, and minimal or no abnormality on the digital rectal exam.
What happens during the procedure?
The entire procedure takes about 90 minutes. Most patients go home the same
A radiation oncologist and urologist perform the procedure. Both
doctors are actively involved in all aspects of the implantation, from the
planning to the post-operative care. During the procedure, the urologist
provides ultrasound guidance and the radiation oncologist places the radioactive
seeds. The prostate ultrasound and treatment planning are both done at the same
time as implantation of the radioactive seeds.
After general or spinal anesthesia, the legs are elevated and padded very
The ultrasound probe is inserted into the rectum and is used to
take pictures of the prostate. The probe remains in place throughout the
The ultrasound images are used to generate an individualized
treatment plan. Then the radioactive seeds are loaded into the designated number
In a specific order, each needle is inserted through the skin in
the perineum (the area between the base of the scrotum and the anus) and into
the prostate using continuous ultrasound guidance. Once accurate needle
placement is confirmed, the seeds in that needle are released. This process is
continued until all of the radioactive seeds have been implanted. No surgical
incision or cutting is necessary.