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Radiation therapy uses high-energy rays or particles to kill cancer
cells. Radiation is sometimes used as the initial treatment for
low-grade cancer that is still confined within the prostate gland or
that has only spread to nearby tissue. Cure rates for men with these
types of cancers are much like those for men getting radical
prostatectomy. Radiation is also sometimes used if the cancer is not
completely removed or comes back (recurs) in the area of the prostate
after surgery. If the disease is more advanced, radiation may be used
to reduce the size of the tumor and to provide relief from present and
possible future symptoms.
Two main types of radiation therapy are used: external beam
radiation and brachytherapy (internal radiation). Both appear to be
good methods of treating prostate cancer, although there is more
long-term information about the results of treatment with external beam
radiation.
External Beam Radiation Therapy
(EBRT)
In EBRT the radiation is focused on the prostate gland from a
source outside your body. It is much like getting an x-ray but for a
longer time. Before treatments start, imaging studies such as MRIs, CT
scans, or plain x-rays of the pelvis are done to find the exact
location of your prostate gland. The radiation team may then make some
ink marks on your skin that they will use later as a guide to focus the
radiation in the right area. You will usually be treated 5 days per
week in an outpatient center over a period of 7 to 9 weeks. Each
treatment lasts only a few minutes and is painless.
Aside from being used as a treatment for early stage cancer,
external beam radiation can also be used to help relieve bone pain when
the cancer has spread to a specific area of bone.
Standard (conventional) EBRT is used much less often than in
the past. Newer techniques allow doctors to be more accurate in
treating the prostate gland while reducing the radiation exposure to
nearby healthy tissues. These techniques appear to offer better chances
of increasing the success rate and reducing side effects.
Three-dimensional conformal radiation therapy
(3D-CRT): 3D-CRT
uses special computers to precisely map the location of your prostate.
You will likely be fitted with a plastic mold resembling a body cast to
keep you in the same position so that the radiation can be aimed more
accurately. Radiation beams are then shaped and aimed at the prostate
from several directions, which makes it less likely to damage normal
tissues.
Although the procedure is fairly new, the short-term results
suggest that it is at least as effective as standard radiation therapy.
Many doctors now recommend using it when it is available. In theory, by
aiming the radiation more accurately, doctors can reduce radiation
damage to tissues near the prostate and cure more cancers by increasing
the radiation dose to the prostate. Long-term study results are still
needed to confirm this.
Intensity modulated radiation therapy (IMRT):
IMRT is an
advanced form of 3D therapy. It uses a computer-driven machine that
actually moves around the patient as it delivers radiation. In addition
to shaping the beams and aiming them at the prostate from several
angles, the intensity (strength) of the beams can be adjusted to
minimize the dose reaching the most sensitive normal tissues. This
allows doctors to deliver an even higher dose to the cancer areas. Many
major hospitals and cancer centers are now able to provide IMRT.
Conformal proton beam radiation therapy:
Proton beam therapy
is related to 3D-CRT and uses a similar approach. But instead of using
x-rays, this technique focuses proton beams on the cancer. Protons are
positive parts of atoms. Unlike x-rays, which release energy both
before and after they hit their target, protons cause little damage to
tissues they pass through and then release their energy after traveling
a certain distance. This means that proton beam radiation may be able
to deliver more radiation to the prostate and do less damage to nearby
normal tissues. As with 3D-CRT and IMRT, early results are promising,
but more studies will be needed to show a long-term advantage over
standard external beam radiation. The machines needed to make protons
are expensive, and there are only a handful of them in use in the
United States. Proton beam radiation may not be covered by all
insurance companies at this time.
Possible side effects of external beam radiation
therapy: The
numbers used in describing the possible side effects below relate to
standard external radiation therapy, which is now used much less often
than in the past. The risks of the newer treatment methods described
above are likely to be lower.
Bowel problems:
During and after treatment with external beam
radiation therapy, you may have diarrhea, sometimes with blood in the
stool, rectal leakage, and an irritated large intestine. Most of these
problems go away over time, but in rare cases normal bowel function
does not return after treatment ends. In the past, about 10% to 20% of
men reported bowel problems after external beam radiation therapy, but
the newer conformal radiation techniques may be less likely to cause
these problems.
Bladder problems:
You might have trouble with having to
urinate often, a burning sensation while urinating, and blood in your
urine. Bladder problems continue in about 1 out of 3 patients, with the
most common problem being the need to urinate often.
Urinary incontinence:
Although this side effect is less common
than after surgery overall, the chance of incontinence goes up each
year for several years after treatment.
Impotence: After
several years, the impotence rate after
radiation is about the same as that of surgery. It usually does not
occur right after radiation therapy but slowly develops over a year or
more. This is different from surgery, where impotence occurs
immediately and may improve over time. In older studies, about 3 out of
4 men were impotent within 5 years of having external beam radiation
therapy (some of these men had erection problems before treatment). In
men who had normal erections before treatment, about half became
impotent at 5 years. It's not clear if these numbers will apply to
newer forms of radiation as well. As with surgery, the older you are,
the more likely it is you will become impotent. Impotence may be helped
by treatments such as those listed in the section above, including
erectile dysfunction medicines.
Feeling tired:
Radiation therapy may also cause fatigue that
may not disappear until a few months after treatment stops.
Lymphedema: Fluid
buildup in the legs or genitals (described
in the surgery section of this document) is possible if the lymph nodes
receive radiation.
Brachytherapy (Internal Radiation Therapy)
Brachytherapy (also called seed implantation or interstitial
radiation therapy) is the use of small radioactive pellets, or "seeds,"
each about the size of a grain of rice, that are placed directly into
your prostate. Brachytherapy is generally used only in men with early
stage prostate cancer that is relatively slow growing.
Its use may also be limited by other factors. For men who have
had a transurethral resection of the prostate (TURP) or for those who
already have urinary problems, the risk of urinary side effects may
higher. Brachytherapy may not be as effective in men with large
prostate glands because many more seeds may be needed. Doctors are now
looking at ways of getting around this, such as giving men a short
course of hormone therapy beforehand to shrink the prostate.
Imaging tests such as transrectal ultrasound, CT scans, or MRI
help guide the placement of the radioactive pellets. Special computer
programs calculate the exact dose of radiation needed. Without these,
the cancer might get too little radiation or the normal tissues around
it could get too much.
There are 2 types of prostate brachytherapy. Both are done in
an operating room and require some type of anesthesia.
Permanent (low dose rate, or LDR) brachytherapy: In this approach, pellets (seeds) of radioactive material
(such as iodine-125 or palladium-103) are placed inside thin needles,
which are inserted through the skin in the area between the scrotum and
anus (perineum) and into the prostate. The pellets are left in place as
the needles are removed and give off low doses of radiation for weeks
or months. Radiation from the seeds travels a very short distance, so
the seeds can put out a very large amount of radiation to a very small
area. This decreases the amount of damage done to the healthy tissues
that are close to the prostate.
Usually, anywhere from 40 to 100 seeds are placed. Because
they are so small, their presence causes little discomfort, and they
are simply left in place after their radioactive material is used up.
This type of radiation therapy requires spinal anesthesia (where the
lower half of your body is numbed) or general anesthesia (where you are
asleep) and may require 1 day in the hospital.
You may also receive external beam radiation along with
brachytherapy, especially if there is a risk that your cancer has
spread outside of the prostate (for example, if you have a high Gleason
score).
Temporary (high dose rate, or HDR) brachytherapy:
This is a newer technique. Hollow needles are placed through
the perineum into the prostate. Soft nylon tubes (catheters) are placed
in these needles. The needles are then removed but the catheters stay
in place. Radioactive iridium-192 or cesium-137 is then placed in the
catheters, usually for 5 to 15 minutes. Generally, about 3 brief
treatments are given, and the radioactive substance is removed each
time. The treatments are usually given over a couple of days. After the
last treatment the catheters are removed. For about a week following
placement of the catheters, you may have some pain in the area between
your scrotum and rectum, and your urine may be reddish-brown.
These treatments are usually combined with external beam
radiation given at a lower dose than if used by itself. The total dose
of radiation is computed so that it is high enough to kill all the
cancer cells. The advantage of this approach is that most of the
radiation is concentrated in the prostate gland itself, sparing the
urethra and the tissues around the prostate such as the nerves,
bladder, and rectum.
Possible risks and side effects of brachytherapy: If you receive permanent brachytherapy seeds, they will give
off small amounts of radiation for several weeks. Even though the
radiation doesn't travel far, your doctor may advise you to stay away
from pregnant women and small children during this time. You may be
asked to take other precautions as well, such as wearing a condom
during sex.
There is also a small risk that some of the seeds may move
(migrate). You may be asked to strain your urine for the first week or
so to catch any seeds that might come out. Be sure to carefully follow
any instructions your doctor gives you. There have also been reports of
the seeds moving through the bloodstream to other parts of the body,
such as the lungs. As far as doctors can tell, this doesn't seem to
cause any ill effects and happens very rarely.
Like external beam radiation, brachytherapy can also cause
impotence, urinary problems, and bowel problems.
Bowel problems: Significant
long-term bowel problems (including burning and rectal pain and/or
diarrhea) occur in less than 5% of patients.
Urinary problems:
Severe urinary incontinence is not a common side effect. But frequent
urination may persist in about 1 out of 3 patients who have
brachytherapy. This is perhaps caused by irritation of the urethra, the
tube that drains urine from the bladder. Rarely, this tube may actually
close off (known as urethral stricture) and need to be opened with
surgery.
Impotence: Problems
with erections may be less likely to develop after brachytherapy than
after other common forms of treatment, but this is unclear. Some
studies have found rates of sexual dysfunction to be lower after
brachytherapy, but other studies have found that the impotence rates
were no lower than with external beam radiation or surgery. Again, the
younger you are and the better your sexual function before treatment,
the more likely you will be to regain function after treatment.
Revised: 06/14/2007
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