Photodynamic therapy, also known as PDT or blue light, is a treatment used for precancerous changes in the skin known as actinic keratosis. Actinic keratosis present as rough, scaly patches on such sun-exposed skin as the face, scalp, ears, and backs of the hands. Untreated, these can progress to form a true skin cancer called squamous cell carcinoma.
PDT uses a topical photosensitizing agent called Levulan®, which is absorbed into the skin. The treated area is exposed to light, which activates a chemical reaction that kills the damaged cells. Some stinging is experienced during the light exposure, but in general, the treatment is well tolerated. Most people develop some redness and scaling for several days to a week after the procedure. Exposure to light needs to be minimized for 48 hours after the procedure. Sunscreens need to be used faithfully during this time period, as well as on an ongoing basis to help minimize further sun damage. Two treatments are recommended for best results.
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PDT can be used in combination with cryotherapy, since lesions can be frozen to diminish their thickness prior to treatment and improve penetration of the Levulan®, leading to better results. Any lesions that do not respond well to PDT can subsequently be treated with cryotherapy or other modalities.
There are several benefits to PDT. The most important is that it treats a larger area than does liquid nitrogen cryotherapy, which is applied on the spot of an actinic keratosis. This allows the blue light to help clear up any actinic keratosis that are developing but not readily identified by the naked eye. This can also be accomplished with prescription topical medications such as 5-fluorouracil, but the treatment and the healing process tend to be much longer, and this may interfere with social activities and professional obligations. In my experience, patients who have had both types of treatments tend to prefer PDT. A recent review compared the effectiveness of PDT versus cryotherapy and found that PDT was more effective than cryotherapy, with a 14 percent better chance of complete lesion clearance at 3 months.
Resolution of actinic keratoses improves the overall appearance and texture of the skin and should reduce the development of squamous cell carcinoma.
Learn more about PTD. Philadelphia-area patients can contact Dr. Elizabeth Spiers' office by calling (215) 230-4592.