VANCOUVER – Indoor simulated daylight photodynamic therapy for actinic keratoses sidesteps the major shortcoming of natural daylight PDT by providing a standardized, dermatologist-controlled light dose that’s not dependent upon the vagaries of weather, season, or outdoor temperature, Dr. Uwe Reinhold reported at the World Congress of Dermatology.
Daylight PDT, in which the photosensitizing agent is activated by natural light, is an increasingly popular concept that originated in Scandinavia but is starting to catch on in the United States. Daylight PDT is less expensive and far less painful than traditional PDT, in which the photosensitizer is activated by a pulsed dye laser or an intense pulsed light device. But on a rainy day or a cold, short, winter day, it can be a problem getting sufficient daylight outdoors to reliably activate the PDT, noted Dr. Reinhold of the Dermatology Center Bonn (Germany) Friedensplatz.
Dr. Reinhold and his colleagues solved that problem by installing a special lamp system on the ceiling of a treatment room in the office. The system enables a dermatologist to simultaneously treat several patients, who receive their 2-hour light dose while seated comfortably in the treatment room reading a book or resting.
Dr. Reinhold presented a retrospective study of 32 patients who underwent simulated daylight PDT (SDL-PDT) in his office. At baseline, the patients had a mean of 5.3 AKs on the scalp and/or face. At follow-up 12 weeks after their second and final SDL-PDT session, they averaged 0.4 AKs. Ninety-three percent of all AKs were cleared, and three-quarters of the patients were completely AK-free.
Traditional PDT is so painful that compliance becomes an issue, Dr. Reinhold noted. In contrast, SDL-PDT, like daylight PDT, is almost pain free. Pain assessment on a 0-10 visual analog scale conducted during the first SDL-PDT session showed mean scores of 0.1, 0.3, and 0.6 at 30, 60, and 90 minutes after illumination began. None of the patients required an analgesic, according to the dermatologist.
The procedure begins with curettage of hyperkeratotic lesions, followed by application of aminolevulinic acid (ALA) gel under occlusion for 30 minutes. Dr. Reinhold uses BF-200 (Ameluz), an ALA manufactured by Biofrontera, a German company, which is popular in Europe but not marketed in the United States. The gel contains 78 mg of ALA per gram. After the 30-minute incubation, the photosensitizer is removed and the special lights are switched on for 2 hours. Protective eye goggles aren’t needed. All patients receive a second treatment session 1 week later.
The lights Dr. Reinhold uses are Indoorlux, marketed by Swiss Red AG. One pair of lights is needed per patient. At a distance of 110-150 cm from the light source, the system produces 15,000-25,000 Lux. The lamps mimic the green and red components of daylight. The combined effective light dose at the wavelengths important in activating protoporphyrin IX so that it can destroy precancerous cells – green/yellow at 570-590 nm and orange/red at 620-640 nm – is 14.3-24.2 J/cm2, depending upon the distance from the light source. That’s comfortably above the 9.4-10.8 J/cm2 other investigators have determined is required for effective natural daylight PDT.
In the United States, however, as in Europe, SDL-PDT is currently an off-label therapy for AK treatment, he noted.
Dr. Reinhold reported serving as a consultant to Biofrontera and receiving speaking fees from the company.