Photodynamic Therapy (cont.)
Gary W. Cole, MD, FAAD
Dr. Cole is board certified in dermatology. He obtained his BA degree in bacteriology, his MA degree in microbiology, and his MD at the University of California, Los Angeles. He trained in dermatology at the University of Oregon, where he completed his residency.
William C. Shiel Jr., MD, FACP, FACR
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
In this Article
- What is photodynamic therapy (PDT)?
- What photosensitizer drugs are available?
- What light sources are available, and how are they applied?
- How does photodynamic therapy work?
- Does PDT make me permanently more sensitive to light?
- How is PDT used to treat the skin?
- What is a typical skin PDT session like?
- How much improvement can I expect with photodynamic therapy?
- Where can I have photodynamic therapy, and who performs the procedure?
- What are the advantages with photodynamic therapy for treating actinic keratoses?
- Am I a good candidate for photodynamic therapy?
- What growths is PDT not good for?
- What are possible complications of photodynamic therapy?
- Is there scarring from photodynamic therapy?
- What are alternatives for photodynamic therapy?
- What about insurance coverage and costs of photodynamic therapy?
- How do I prepare for my procedure?
- How is recovery after photodynamic therapy (PDT)?
- Is there pain after PDT?
- How do I take care of my treatment area after photodynamic therapy?
- What is the chance that my actinic keratoses will recur?
- Find a local Dermatologist in your town
What photosensitizer drugs are available?
FDA-approved photosensitizers include porfimer sodium (Photofrin), 5-aminolevulinic acid or ALA (Levulan), and methyl aminolevulinate [MAOP] (Metvix). More drugs may become available in the near future. Photofrin is used intravenously for internal cancers while Levulan and Metvix are applied topically for skin therapy.
What light sources are available, and how are they applied?
PDT light sources include laser, intense pulsed light, light-emitting diodes (LEDs), blue light, red light, and many other visible lights (including natural sunlight). Photosensitizer drugs may become activated by one or several types of light. The optimal light depends on the ideal wavelength for the particular drug used and target tissue.
The light source needs to be directly applied to the target tissue for a specific amount of time. For surface skin treatments, the light is easily directly applied to the area of the skin where the photosensitizer drug has been applied (such as face, scalp, arms, etc.). For internal cancers, delivering the light to the desired area is more challenging. The light may be delivered through small fiber-optic cables into the body cavity or area being treated. Sometimes, endoscopes (a thin, lighted, elongated tube that is inserted into a body space) are used to deliver the light into the lungs, stomach, or bladder.
How does photodynamic therapy work?
PDT works by direct injury to the target cells and tissues. This involves an activated oxygen molecule that can injure or destroy nearby cells. Because the normal skin barrier is not present at the sites of the actinic keratoses, it is preferentially absorbed there and activated by light. Then, the activated oxygen destroys the adjacent abnormal tissue. Once the areas have healed following PDT, the areas are reexamined to see if additional treatments or biopsies are needed.
With traditional cryosurgery (freezing with liquid nitrogen), only the visible actinic keratoses can be treated. Since many actinic keratoses are often not evident, this PDT might be preferable since it presumably would destroy these "subclinical" lesions. PDT allows for treatment of an entire area of sun damage simultaneously, but subsequent treatments may be necessary.
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