Photodynamic

Therapy

Ishaque PK
123680033
Synonyms…
• Photoradiation therapy,
• Phototherapy,
• Photochemotherapy.

Defenition…
• Photodynamic therapy or PDT is a treatment that uses
special drugs, called photosensitizing agents, along
with light to kill cancer cells. The drugs only work
after they have been activated or “ turned on” by certain
kinds of light.
 What is photodynamic therapy?
• 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, photoactivation causes the formation
of singlet oxygen, which produces peroxidative reactions
that can cause cell damage and death.
• Each photosensitizer is activated by light of a specific
wavelength. This wavelength determines how far the
light can travel into the body.
How is PDT used to treat cancer?
• In the first step of PDT for 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.
– The photosensitizer can damage blood vessels in the tumor,
thereby preventing the cancer from receiving necessary 
nutrients.
– PDT also may activate the immune system to attack the
tumor cells.
Action……
• The light used for PDT include laser, intense pulsed
light, light-emitting diodes (LEDs), blue light, red
light, and many other visible lights (including natural
sunlight). 
• 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
• Extracorporeal photopheresis (ECP) is a type of
PDT in which a machine is used to collect the
patient’ s blood cells, treat them outside the body with
a photosensitizing agent, expose them to light, and
then return them to the patient.
• The U.S. Food and Drug Administration (FDA) has
approved ECP to help lessen the severity of skin
symptoms of cutaneous T-cell lymphoma that has not
responded to other therapies.
• Studies are under way to determine if ECP may have
some application for other blood cancers, and also to
help reduce rejection after transplants.
 What types of drugs and cancer
are currently treated with PDT?
Porfimer sodium (Photofrin®)
• Porfimer sodium is the most widely used and studied
photosensitizer.
• It’ s activated by red light from a laser. It’ s approved
by the FDA to treat patients with: Cancer of the
esophagus (the swallowing tube).
• Barrett esophagus, a pre-cancerous condition that may
lead to esophageal cancer in people who don’ t have
surgery.
• A type of non-small cell lung cancer that affects the lining of the
large breathing tubes (the bronchi) called endobronchial cancer.
Benzoporphyrin derivative (BPD verteporfin).
Aminolevulinic acid (ALA or Levulan®):
• Aminolevulinic acid is a drug that’ s put right on the skin. It’ s
used to treat actinic keratosis (AK), a skin condition that can
become cancer, and is used only on the face or scalp. A special
blue light, rather than laser light, is used to activate this drug.
Methyl ester of ALA (Metvixia® cream):
• A disadvantage of the older forms of ALA is that they do not get
into the cancer cells very easily.
• It was approved by the FDA in July 2004 for treatment of some
types of actinic keratoses of the face and scalp. Methyl ester of
ALA is activated with a red light.
Advantages…
It has some advantages, such as:
• It has no longterm side effects when used properly.
• It’ s less invasive than surgery.
• It usually takes only a short time and is most often done as an
outpatient.
• It can be targeted very precisely.
• Unlike radiation, PDT can be repeated many times at the same
site if needed.
• There’ s little or no scarring after the site heals.
• It often costs less than other cancer treatments.
What are the limitations of PDT?
• The light needed to activate most photosensitizers
cannot pass through more than about one-third of an
inch of tissue (1 centimeter).
• For this reason, PDT is usually used to treat tumors on
or just under the skin or on the lining of internal organs
or cavities.
• PDT is also less effective in treating other tumors,
because the light cannot pass far into these tumors.
• PDT is a local treatment and generally cannot be used
to treat cancer that has spread (metastasized).
complications or side effects?
• Drugs makes the skin and eyes sensitive to light for
approximately 6 weeks after treatment.(Thus, patients
are advised to avoid direct sunlight and bright indoor
light for at least 6 weeks.)
• Photosensitizers tend to build up in tumors and the
activating light is focused on the tumor. As a result,
damage to healthy tissue is minimal.
• However, PDT can cause burns, swelling, pain, and
scarring in nearby healthy tissue.
• Other side effects include coughing, painful breathing,
trouble swallowing, stomach pain, or shortness of
breath; these side effects are usually temporary.
 Future hold for PDT…
• Researchers continue to study ways to improve the
effectiveness of PDT and expand it to other cancers. 
• Clinical trials (research studies) are under way to evaluate
the use of PDT for cancers of the brain,
skin, prostate, cervix, and peritoneal cavity (the space in
the abdomen that contains the intestines, stomach, and liver).
• Other research is focused on the development of
photosensitizers that are more powerful, more specifically
target cancer cells, and are activated by light that can
penetrate tissue and treat deep or large tumors.
• Researchers are also investigating ways to improve
equipment and the delivery of the activating light.
References…
• Dolmans DE, Fukumura D, Jain RK. Photodynamic
therapy for cancer. Nature Re vie ws Cance r 2003;
3(5):380–387.
• Wilson BC. Photodynamic therapy for cancer:
principles. Canadian Jo urnal o f Gastro e nte ro lo g y
2002; 16(6):393–396.
• Vrouenraets MB, Visser GW, Snow GB, van Dongen
GA. Basic principles, applications in oncology
and improved selectivity of photodynamic
therapy. Anticance r Re se arch 2003; 23(1B):505–
522.