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have been many studies to determine how much
radiation should be given. In all of the controlled
studies (conducted through the Radiation Therapy Oncology
Group) no one specific radiation dose schedule has shown
a difference in the long-term survival of the patients.
Perhaps more importantly, patients who were treated over
a shorter time and with a larger radiation dose
per treatment had a quicker response. However,
they were also hampered with more severe side effects
of the treatment if they lived longer.
The
major long-term impact of whole brain irradiation
is decreased memory, slowed thinking processes
and delayed or slowed speech. These are worsened
if chemotherapy has been given before or during
treatment.
In
an effort to try to reduce the problems
that whole brain irradiation creates, the use
of focused radiation (especially that known as
linac-based radiosurgery or the gamma knife), has been
used. This has also been shown to have excellent
control rates in the areas that are treated. Often
patients who have active cancer outside of the brain
and are treated only with local focused radiation have
an excellent quality of life during the remaining time
that they may live.
At
the present time there are no completed randomized
trials that have looked at the difference between
radiosurgery and whole brain irradiation.
It is generally understood that for patients who have
the best chance for long term survival, whole brain
irradiation with focal boost and/or surgery
to symptomatic areas may offer the best ability
to reduce the risk of developing neurological problems
at the end of life.
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