Brachytherapy (Seed Implantation)
In order to treat prostate cancer, radioactive Iodine-125 or Palladium-103
seeds are placed directly into the prostate gland, using either afterloading
needles with a specialized "gun" or preloaded needles. Both of these seeds
give off low-energy x-rays, and the majority of the radioactivity is released
within a short period of time. Only a small volume of prostate tissue
is irradiated by each seed, and therefore many seeds have to be placed
throughout the prostate to cover the entire gland and the cancer site.
Because of the low x-ray radiation energy released, radiation exposure
to adjacent normal organs is reduced. The entire prostate gland is treated
by the radioactive seeds because the microscopic cancer cells may be present
at different sites within the gland, even though the biopsy in the general
area was negative. The number of seeds implanted into the prostate for
treatment depends on the size and shape of the prostate gland. On average,
the number of seeds implanted is approximately 100.
In performing brachytherapy, the doctor places a biplaner ultrasound
probe in the rectum to image the prostate. The biplaner ultrasound, along
with fluoroscopy, gives a multidimensional view of the prostate on several
TV screens. These images are then used to accurately place the needles
and to space the seeds in the prostate gland. No surgical incision is
required. Needles are advanced though an area of skin (behind the scrotum
and in front of the rectum) into the prostate with the aid of (1) a template
attached to the ultrasound probe and (2) a computer plan designed specifically
for the size of the patient’s prostate. Radioactive seeds are then deposited
through the needle into the prostate gland. The seeds are permanently
placed in the prostate gland. Depending on the radioactive seeds that
are selected, they give off radiation for 3 months to a year. Both the
probe and needles are removed when the procedure is completed. Cystoscopy
may then be done, if necessary, to evaluate the urethra and the bladder
and to retrieve any seeds found in the bladder.
If you choose I-125 seed implantation,
you should consider the following:
- Some patients may experience burning or discomfort when urinating
which may last from a few days to several weeks.
- Some patients may experience urinary some frequency and urgency. There
are medications to decrease these side effects. When the swelling subsides,
so do the side effects, usually within 2 months.
- The best results occur when an ultrasound machine is used to depict
a three-dimensional image of the prostate.
- There is no long-term incontinence.
- Brachytherapy is usually less costly than radical prostatectomy or
external beam radiation.
- A procedure that combines ultrasound and fluoroscopy is used to achieve
a satisfactory distribution of seeds.
- An interactive computer and a CT scan are used to assure accurate
seed placement and distribution, which is critical to the success of
the treatment.
- This procedure can be repeated.
- Brachytherapy is sometimes accompanied by external beam radiation,
combination hormonal therapy, or both.
- The procedure does not require a hospital stay, and it usually takes
2 to 3 hours.
- It does not require general anesthesia.
- Patients who have Stage A and B prostate cancer and who have small
tumors are the best candidates.
- Because they are placed at the site of the cancer, the seeds can deliver
two or three times more concentrated radiation to the prostate gland
than can external beam radiation, which must use a lower dose because
it also affects healthy tissue.
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