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The most common prostate cancer
treatment, radiation therapy’s oldest form is
electron beam; newer versions are intensity modulated,
3D-CRT, and proton beam therapy. Experimental treatment
uses neutron beams.
What is Radiation Therapy
for Prostate Cancer?
There are two types of radiation treatment available
to prostate cancer patients: external and brachytherapy.
External therapy has been in medically-effective practice
for longer than brachytherapy. This treatment is often
referred to as radiotherapy. EBRT has been so commonly
used that EBRT and radiation therapy are sometimes used
interchangeably.
The goal of treatment is to irradiate
a targeted area with as much energy as possible while
avoiding the neighboring organs. Intensity modulated
radiation therapy (IMRT) and 3 dimensional conformal
radiation therapy (3D-CRT) are newer versions of EBRT
that better achieve this goal. Proton beam therapy is
becoming a more widely accepted treatment for prostate
cancer, while neutron beam therapy is still in the experimental
stages.
Why does Radiation Therapy
Work on Prostate Cancer?
Radiation is used as a prostate cancer treatment because
high energy waves damage the DNA of cells. If a cell
divides prior to repairing the damage, the cell will
die. Since cancerous cells divide more rapidly than
healthy cells, carefully aimed energy will cause their
destruction.
However, prostate cancer radiation
treatment will last over a period of 5 to 9 weeks. During
this process, the healthy cells that are repeatedly
exposed will be unable to repair the extensive damage.
Therefore, the precise aiming of the beam is crucial
to the success of the treatment and the avoidance of
side effects.
How do these radiation treatments
differ from one another?
Prostate cancer radiation treatment can be divided into
three categories based on the high-energy wave they
use. EBRT, IMRT, and 3D-CRT accelerate subatomic particles
called electrons to generate waves of high energy photon
radiation. Proton beams use a subatomic particle called
protons. Neutron beam therapy uses the subatomic particles
called neutrons. To continue reading about the different
types of subatomic particles, go to the Tools section.
The History of Radiation
Therapy
Prostate cancer radiation treatment has been used in
the United States since 1915. The first radiotherapy
used radium applicators positioned adjacent to the prostate
gland; unfortunately, this technique resulted in significant
morbidity. The next technique in radiotherapy used electron
beam x-rays; however, these x-rays could not penetrate
deeply enough to irradiate the affected tissue. The
x-rays were used mainly for palliative care because
they also caused skin cancer.
After World War II, doctors were
able to use megavoltage in prostate cancer treatment.
They used radioactive isotopes from Cobalt 60. But by
the 1980’s, radiation oncologists began using
the linear accelerator which increased the speed of
particles and allowed for the most process aiming of
the beam.
Fractionated Prostate Cancer
Radiation Treatment
External beam radiation is sometimes called fractionated,
meaning that small doses are given over a long period
of time. Patients receive radiotherapy once a day, Monday
through Friday over 5-9 weeks, depending on the patient.
Normal prostate cells can repair the damage of a small
amount of radiation fairly quickly. Cancerous cells
cannot. Receiving a small dose everyday helps to minimize
the damage sustained by the healthy cells of the surrounding
organs. Giving patients the weekend off helps their
body to recover enough to withstand the next five days
of treatment.
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