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If surgery reveals certain clues that the cancer may have spread, the patient may be
referred for additional treatment.
That brings us to the third treatment approach...radiation therapy.
The goal of radiation therapy is to get as high a dose of radiation into the prostate
gland as possible, while respecting the tolerance of the bladder and ***.
Radiation can be given in a number of ways.
The first form of radiation treatment is called external beam radiation, where radiation is
delivered by a machine called a linear accelerator.
Treatment is given daily... approximately ten minutes per day, Monday through Friday,
over a course of treatment that spans approximately two months.
External beam radiation therapy is delivered using a technique called Three- Dimensional
Conformal Therapy.
With this technique, the patient undergoes a CT scan of the pelvis in an effort to clearly
outline where his prostate is, as well as the normal tissues such as the bladder or
the ***.
Special software programming is used to devise a treatment plan that will maximize the amount
of radiation to the tumor and prostate gland while minimizing damage to the normal, nearby
tissues.
External beam radiation treatment is limited due to the proximity of the bladder and the
***, and currently a dose of 78-8100 centigray is the highest that can safely be achieved
with this approach.
External radiation is delivered using a technique called Intensity Modulated Radiation Therapy
with image guidance.
This is a highly sophisticated way of delivering radiation to the target tissue that allows
for a major reduction in the dose of radiation that hits the *** and bladder.
By using IMRT, we can get a higher dose of radiation into the prostate gland more safely
than we ever could before.
This leads to a better chance of beating the disease, and less chance of injuring the ***
or bladder.
It has been made possible by powerful new computers and the introduction of the dynamic
MLC, or multi-leaf collimator, 120 thin lead leaves that move across the radiation field,
finely tuning the radiation to hit the target and miss the nearby structures.
With the use of IMRT, the radiation can be painted across the region treated with excellent
control.
Due to the fact that the prostate may move as much as an inch in any direction from day
to day, due to *** filling or gas, we have improved our ability to target the prostate
through a process known as image guided radiation, or IGRT.
IGRT deals with the fact that the prostate may move through a variety of different approaches.
In one approach used with the Tomotherapy treatment machine, and with the Cone Beam
CT on the linear accelerator, the patient is setup each day with a CT scan that can
clearly identify the location of the prostate immediately before starting the treatment
beam.
Another approach is the implantation of markers in the prostate by the urologist before starting
the planning process.
These markers are implanted in a similar fashion to the way the original biopsies were performed,
in the urologist’s office using the ultrasound unit.
There are several types of markers.
Some are inert gold markers, or fiducials that can be imaged each day immediately prior
to treatment.
Others are radiofrequency transmitters that can send a signal to the treatment machine,
allowing for small movements of the patient to bring him into perfect alignment for treatment.
The goal of all these approaches is to clearly identify the exact location of the prostate
at the time of treatment, thereby allowing for the best possible targeting of the radiation
beams.
Research is also being done to try to reduce the overall time necessary to treat patients
with external beam radiation in a much shorter overall time period.
Currently, patients who are being treated with IGRT approaches require approximately
8 weeks of daily treatments.
A process known as Stereotactic Body Radiotherapy (SBRT) is being developed which may allow
for external beam treatment to be delivered in as few as five treatment days.
The long term safety of these approaches is currently being tested.
Several other approaches, alternatives to standard radiation therapy, have been developed
or are under development.
Remember, the whole idea is to get as high a dose as possible of radiation into the prostate
without injuring the *** or bladder. Each of these approaches has its own advantages
and drawbacks which should be considered separately.
One such approach is the implantation of permanent radioactive seeds.
The seeds are made of substances such as palladium or iodine that give off a very intense but
localized dose of radiation.
They are placed in the prostate gland, under anesthesia, using needles guided by ultrasound.
These needles pass through the perineum -- the skin in front of the *** and behind the testicles
-- into the prostate.
The procedure itself takes approximately one hour.
During that time a range of from 60 to 120 tiny seeds are placed throughout the prostate
gland.
They are spaced uniformly, except in the central region, where an attempt is made to put fewer
seeds to spare the urethra from any significant radiation injury.
These seeds stay in place and give up their dose of radiation over several months.
The radiation is very intense, but localized to a small area.
The seeds are linked together in absorbable strand material so they cannot migrate to
other sites in the body.
For some patients with very early disease, implantation of these radioactive seeds by
itself is sufficient therapy.
For other patients, however, with more advanced disease, a combination of the seed implants
plus external radiation therapy may be necessary to achieve better control.
Another treatment approach is called a temporary seed implant.
In this procedure, long, thin plastic tubes are inserted into the prostate gland, once
again through the perineum, using ultrasound guidance.
These tubes stay in place in the patient for approximately 30 hours.
While they’re in the patient, a tiny radioactive seed attached to a steel cable is inserted
into the catheters on either three or four occasions during a two-day stay at the hospital.
The seed itself spends only 10-15 minutes within the patient, and then is retracted
into a lead safe.
After each treatment the patient is returned back to his room where he lies flat in bed
until the next treatment.
After the final treatment the catheters are removed and he’s watched for about two hours
before being discharged home.
This approach, called the Temporary High Dose Rate Implant, is most often used in combination
with external beam radiation therapy.
Depending on their stage of disease, a patient may be treated with a permanent seed implantation
alone, external beam radiation therapy alone, or a combination of the two.
A third approach to increasing the does of radiation is to use special radiation beams
of a type different than those produced by a standard linear accelerator such as this
one.
For example, a proton accelerator is used to deliver protons to the prostate.
This is performed as an outpatient procedure.
The goal of proton therapy, as with image guided radiation therapy and brachytherapy,
is to get as high a dose of radiation as possible into the prostate gland, as safely as possible,
trying to limit the risk to the nearby *** and bladder.