Photodynamic therapy, or “PDT”, is a therapy in which a chemical is applied to the skin and left to dry for some time and the skin is then exposed to a light source. PDT is used to treat many condition, including wet age-related macular degeneration, pre-cancers of the skin (actinic keratosis), basal cell carcinoma, acne, and the changes associated with photo-aging.
- Aminolevulinic acid (ALA) is applied to the skin.
- A waiting period of one or more hours must occur to allow for the ALA to be converted into protoporhyrin IX in the skin.
- The skin is exposed to a bright light, which can last seconds to 16 minutes.
- After treatment, the patient must avoid excessive exposure to sunlight for several hours or more.
In the United States, Levulan® Kerastic® is FDA approved for the treatment of actinic keratosis, or pre-cancers. Although, this treatment has been used for the treatment of superficial basal cell carcinoma and squamous cell carcinoma in situ, but this remains an off-label indication.There is moderate discomfort with the treatment, which may not be well tolerated by many.