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Laser
Center -
Photodynamic Therapy
for Cancer Treatment
Understanding Photodynamic Therapy Photodynamic therapy, or PDT, is a relatively
new, two-step, cancer treatment which uses a light-sensitive drug and laser beam to destroy cancer
cells. The photosensitive drug accumulates in malignant cells and is
harmless until exposed to a low-intensity, visible red light.
In the United States PDT is used for the
palliative treatment of advanced esophageal cancer and recently, the Food and Drug Administration approved it
as a potentially curative treatment for certain types of
early-stage microinvasive lung cancer. PDT is also approved for various applications
worldwide including Canada (bladder and
esophageal cancer), The Netherlands (lung and esophageal cancer), and Japan (early lung cancer).
How does PDT work?
The first step of treatment is an injection of a nontoxic drug called
Photofrin (porfimer sodium). Given intravenously, this drug is
absorbed by both normal and malignant cells. However, 40-50 hours after the injection,
the amount of light-sensitive drug is concentrated
in cancer cells and reduced in normal
cells. In the second step, laser light is applied to the tumor approximately two
days following injection. This light generates no heat, but
activates the Photofrin, causing an almost immediate destruction of tumor cells.
Depending on the treatment site, this step may be performed in a surgical suite at the
hospital requiring a short stay, or done on an outpatient basis.
What are the benefits of
PDT?
PDT is particularly valuable in treating tumors which resisted conventional
forms of therapy. Previous surgery, radiation, or chemotherapy do not
restrict its use.
PDT is a localized form of treatment so it
limits damage to surrounding healthy tissue. It does not cause a cumulative toxic effect, and can be
repeated if tumor growth recurs.
To maximize effectiveness PDT may also be
used in conjunction with other treatments such as surgery, radiation, or chemotherapy.
Although PDT is beneficial in treating localized cancers, it is generally
not used when cancer has metastasized or spread to other areas of the body.
This is also true for most leukemias and
lymphomas, which are considered systemic diseases involving the blood, bone marrow or lymphatic system.
What can be expected with PDT?
Local swelling and inflammation may occur
around the treatment site causing discomfort in the chest. Due to the photoactive nature of the drug, there
will be a sensitivity to bright light for four to six weeks following
injection at the first stage of treatment. During this time, eyes and skin
should be protected from sun rays, bright lights like reading lamps or those
used in a dentist's office, and helmet-type hairdryers. Exposure to direct
sunlight should be avoided, but when outdoors, sunglasses and full
protective clothing must be worn. Brief exposure to strong light can cause
redness and swelling until the drug clears completely from the skin cells.
Additional side effects may include nausea, fever, or constipation.
Further
Information
Determining if this treatment is right for your particular type of cancer
requires the judgment and knowledge of a physician.
To find out if photodynamic therapy will benefit your situation, you should
speak with your oncologist. He or she may refer you to the physicians
credentialed for photodynamic therapy. Write any questions you have so you
can discuss them with your doctor. If you
need further assistance, please contact the Laser Center at (218) 733-2333.
If your oncologist wishes to consult with a physician credentialed to
perform photodynamic therapy, he or she may
contact:
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Dr. John Streitz
Duluth Clinic Thoracic and
Cardiovascular Surgery
(218) 722-8364
Dr. Michael Van Norstrand
Duluth Clinic Gastroenterology
(218) 722-8364
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This information is not intended as a
substitute for professional medical advice. Only your doctor can diagnose and treat a
medical problem.
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