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External radiation delivered from a high energy X-ray machine called a linear accelerator has been effectively
used to treat prostate cancer for more than 30 years. In recent years, there have been several major technological advances
allowing cure rates that typically exceed those of surgery and proton beam therapy, with far fewer side effects. With
intensity modulated radiation therapy (IMRT), sophisticated computers modulate the intensity of the radiation beam, increasing
it to areas where cancer cells reside, and decreasing it to areas that need to be protected. This allows for maximum radiation
to be delivered to the prostate and areas potentially harboring cancer cells, while minimizing radiation to the bladder and
rectum. Patients with intermediate to advanced stage prostate cancer have a high risk of having cancer outside the prostate,
beyond the surgeon’s reach. Unlike surgery, IMRT can treat this area.
Image Guided Radiation Therapy (IGRT) takes IMRT one step further. Various imaging technologies such as Cone-beam®
CT scan, tracking of implanted fiducial markers, or BAT® ultrasound imaging, are utilized before each daily
treatment, to acquire an image of the prostate and surrounding anatomy. Computers detect any slight change in position of
the prostate gland that may result from movement or variations in filling of the bladder or rectum. Using this information,
the computer adjusts the radiation beam accordingly in order to precisely target the treatment to the prostate’s exact
position that day. Changes as small as 1 millimeter are allowed to provide the greatest precision available. IGRT is the newest
and most advanced system for the delivery of radiation, allowing much greater precision than proton therapy.
Prior to beginning IGRT treatment, our patients undergo a special CT and MRI scan of the pelvis in our department.
This scan is used to create a customized plan, tailored to fit each patient’s anatomy precisely. IGRT is typically given
for only a few minutes a day, five days a week. When combined with a seed implant, this part of the treatment is approximately
5 weeks long. If given without a seed implant, the treatment is typically for 8 1/2 weeks. IGRT is completely painless
and non-invasive. During treatment, the most commonly reported side effects are slight fatigue and having to go to the bathroom
more frequently. You will NOT develop any nausea, abdominal pain, hair loss, or skin burning. You will NOT lose your ability
to control your bowels or bladder. You will be able to continue working full-time and should enjoy all of your regular activities. Patients
with more aggressive or advanced stages of cancer have a higher than ideal risk of cancer outside the prostate. This is an
area beyond the surgeon’s reach. IGRT can help treat just outside the prostate, where the prostate cancer cells may
reside. Using the latest computer technology, the prostate can be precisely targeted within the body, and radiation can be
safely delivered.
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A recent study from the largest proton center in the country at Loma Linda, California reported that for 1,225 men with
prostate cancer, the 5-year success rate with proton therapy was only 73%. For those with high risk disease, the success rate
was only 43% (Slater, 2004) Tnfortunately, there have not been any studies looking at outcomes more than 5 years following proton beam treatment. This
is in comparison to our own recently reported long term study showing at 10 years, a 95% success rate with seed implants for
intermediate risk disease, and 83% success rate for high risk disease (Terk 2009).
With the seeds being placed directly in the prostate, higher doses of radiation can be given to the cancer, resulting in
a much higher BED (biologically effective dose). The 20-50% higher BED seen with seed implants results in much greater cancer
killing. Seed implants allow the ultimate concentration of radiation directly in the prostate, while still keeping surrounding
areas at the lowest dose possible
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