Radiation Oncology—Prostate Seed
Implantation
After a diagnosis of prostate cancer has been established
with a biopsy, the patient should discuss the treatment options with
a radiation oncologist and a urologist. Radiation therapy treatment options
to cure prostate cancer include:
- External beam radiotherapy
- Prostate brachytherapy (permanent seed implants,
High Dose rate temporary implants
External Beam Radiotherapy
External beam radiotherapy
involves a series of daily outpatient treatments to accurately deliver
radiation to the prostate.
Intensity modulated radiation therapy or
IMRT is the most recent advance in the delivery of radiation. This
technique allows very precise adjustment of radiation doses to the
tissues within the target area, potentially allowing an increased radiation
dose to the prostate and reduced doses to nearby normal tissues such as
rectum and bladder. Higher doses to the prostate translate into a greater
chance for cure, while lower doses to surrounding organs mean fewer
side effects.
IMRT radiation treatments are delivered in a series of
daily sessions, each under half-hour in duration, Monday through Friday
for seven to ten weeks overall.
At St. Agnes Cancer Center prostate IMRT is implemented
utilizing TomoTherapy HiArt System® technology. This unique
system combines a radiation therapy source (linear accelerator)
and CT into a single unit. Radiation therapy is delivered continuously
in a spiral fashion spreading the dose around the treated area.
Daily real-time CT imaging allows for the most precise targeting
available.
Potential side effects, including fatigue, increased
frequency or discomfort of urination, and proctitis, typically resolve
within a few weeks after completing treatments. Impotence is also a potential
late side effect of any treatment for prostate cancer. However, many
patients who receive radiation therapy for prostate cancer are able
to maintain sexual function.
Prostate Brachytherapy
Prostate brachytherapy, better
known as a seed implant, is often done in the operating room. There
are two methods of delivering internal radiation for prostate cancer:
- Permanent
seed implants. These treatments are designed to deliver a very
high dose of radiation to the tumor by inserting radioactive seeds directly
into the prostate gland under ultrasound guidance while the patient
is under anesthesia. Isotopes of iodine or palladium are most commonly
used. The seeds are approximately four millimeters long and less
than a millimeter in diameter. In certain situations, both prostate
brachytherapy and external radiation may be recommended to combat
the tumor.
- High-dose
rate temporary implants. Devices called high dose rate remote afterloading
machines allow radiation oncologists to complete brachytherapy
over 10 to 20 minutes in 2 or 3 sessions. Powerful radioactive
sources travel through small tubes called catheters to the prostate
gland for the amount of time prescribed by your radiation oncologist.
You may be able to go home shortly after the procedure. No seed
remains in the patient after the treatment is completed.
The side effects
from seed implants are similar to those experienced with external
beam radiotherapy. Patients usually experience urinary frequency
and discomfort in urination. These effects may be lessened with medications
and usually dissipate over the course of three to six months.
Hormone Therapy
Certain patients may benefit from hormone
therapy in addition to radiation. In some patients, hormone therapy works
with radiation therapy to improve cure rates.
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