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Photodynamic
therapy
(PDT) is a
treatment
that uses
a drug,
called a
photosensitizer
or
photosensitizing
agent, and
a
particular
type of
light.
When
photosensitizers
are
exposed to
a specific
wavelength
of light,
they
produce a
form of
oxygen
that kills
nearby
cells.
Each
photosensitizer
is
activated
by light
of a
specific
wavelength.
This
wavelength
determines
how far
the light
can travel
into the
body.
Thus,
doctors
use
specific
photosensitizers
and
wavelengths
of light
to treat
different
areas of
the body
with PDT.
PDT
cancer
treatment
In the
first step
of PDT for
skin cancer
treatment,
a
photosensitizing
agent is
injected
into the
bloodstream.
The agent
is
absorbed
by cells
all over
the body,
but stays
in cancer
cells
longer
than it
does in
normal
cells.
Approximately
24 to 72
hours
after
injection,
when most
of the
agent has
left
normal
cells but
remains in
cancer
cells, the
tumor is
exposed to
light. The
photosensitizer
in the
tumor
absorbs
the light
and
produces
an active
form of
oxygen
that
destroys
nearby
cancer
cells.
In
addition
to
directly
killing
cancer
cells, PDT
appears to
shrink or
destroy
tumors in
two other
ways (1,
2, 3, 4).
The
photosensitizer
can damage
blood
vessels in
the tumor,
thereby
preventing
the cancer
from
receiving
necessary
nutrients.
In
addition,
PDT may
activate
the immune
system to
attack the
tumor
cells.
The light
used for
PDT can
come from
a laser or
other
sources of
light.
Laser
light can
be
directed
through
fiber
optic
cables
(thin
fibers
that
transmit
light) to
deliver
light to
areas
inside the
body. For
example, a
fiber
optic
cable can
be
inserted
through an
endoscope
(a thin,
lighted
tube used
to look at
tissues
inside the
body) into
the lungs
or
esophagus
to treat
cancer in
these
organs.
Other
light
sources
include
light-emitting
diodes (LEDs),
which may
be used
for
surface
tumors,
such as
skin
cancer.
PDT is
usually
performed
as an
outpatient
procedure.
PDT may
also be
repeated
and may be
used with
other
therapies,
such as
surgery,
radiation,
or
chemotherapy.
What types
of cancer
are
currently
treated
with PDT?
To date,
the U.S.
Food and
Drug
Administration
(FDA) has
approved
the
photosensitizing
agent
called
porfimer
sodium, or
Photofrinฎ,
for use in
PDT to
treat or
relieve
the
symptoms
of
esophageal
cancer and
non-small
cell lung
cancer
(7).
Porfimer
sodium is
approved
to relieve
symptoms
of
esophageal
cancer
when the
cancer
obstructs
the
esophagus
or when
the cancer
cannot be
satisfactorily
treated
with laser
therapy
alone.
Porfimer
sodium is
used to
treat
non-small
cell lung
cancer in
patients
for whom
the usual
treatments
are not
appropriate,
and to
relieve
symptoms
in
patients
with
non-small
cell lung
cancer
that
obstructs
the
airways.
In 2003,
the FDA
approved
porfimer
sodium for
the
treatment
of
precancerous
lesions in
patients
with
Barretts
esophagus
(a
condition
that can
lead to
esophageal
cancer).
PDT
For Acne
Treatment
Severe
acne can
sometimes
require
high-power
treatments.
There is a
procedure
that
treats
active and
resistant
acne that
combines a
special
light-activated
solution
that
targets
and
destroys
acne
activity.
This
treatment
can also
diminish
older acne
scars,
leaving
your skin
with a
much
smoother
appearance.
The
procedure
is called
Photo
Dynamic
Therapy.
Photodynamic
Acne
Treatment
(PDT) is a
process by
which a
photosensitizing
agent is
applied to
your skin.
A
photosensitizing
agent is a
special
solution
applied to
the skin
that is
activated
by a
specific
wavelength
of light.
Photosensitizing
agents
have been
used
extensively
for the
treatment
of a
variety of
different
skin
conditions.
Levulan is
a 20%
solution
of
Aminolevulinic
Acid
(ALA). ALA
is a
natural
product
found in
all humans
throughout
the body.
It is a
precursor
for
hemoglobin
synthesis.
PDT-ALA is
a
procedure
that can
significantly
improve
moderate
to severe
acne,
including
cystic
acne.
Prior to
Photodynamic
Acne
Treatment,
the best
available
treatment
option for
resistant
and cystic
acne was
Accutane.
However,
with
Accutane
there are
many
systemic
side
effects
including
birth
defects,
liver
abnormalities,
mood
depression,
and
virtually
all
patients
get
dryness
and night
vision
changes.
PDT
Acne
Treatment
provides a
viable
alternative
to
Accutane
as there
are no
systemic
effects.
Three to
five
treatments
are
advisable
at two to
three week
intervals
to obtain
optimal
results.
Additional
benefits
of ALA PDT
may
include:
-
Improvement
of
sun
damage
and
brown
spots
-
Some
improvement
of
fine
lines
and
wrinkles
-
Improvement
of
uneven
skin
pigmentation
-
Slight
reduction
in
pore
size
-
Slight
improvement
of
Rosacea
bumps
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