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Photodynamic therapy: More bang from each dose

Article-Photodynamic therapy: More bang from each dose

A cosmetic version of PDT would help to optimize esthetic effects and repair sun-damaged cells, according to Dr. David Mendes. (Photos: David Mendes, M.D).
New Orleans — Photodynamic therapy (PDT), traditionally used for skin diseases, also functions as a rejuvenation technique, according to David Mendes, M.D.

"This is a new application for PDT," Dr. Mendes says. "We've seen that it reverses the signs of photodamage, is well-tolerated by patients, and may also delay the onset of some future skin malignancies."

Dr. Mendes is a plastic surgeon at the Chaim Sheba Medical Center in Tel Hashomer, Israel, where he collaborates with laser expert Arie Orenstein, M.D.

He explains, "After treating patients with lesions over a broad area of the face, we observed a therapeutic, superficial rejuvenation effect on the skin."

To get a closer look, he evaluated photographic records and charts at Sheba's Advanced Technologies Center, selecting cases randomly from thousands of patients receiving PDT treatment for conditions such as basal cell carcinoma, actinic keratoses and Bowen's disease.

"It was clear that people who had PDT treatment for purely medical reasons had a positive side effect: They looked better," he says.

Dermatologists are already working in this area, but it's a new idea for esthetic surgeons. The future challenge, Dr. Mendes says, is optimizing protocols. After that, he plans to develop training modules to help plastic surgeons adopt PDT.

"There are plenty of plastic surgeons with experience using lasers and skin-peeling procedures," he notes. "This is a related modality using natural substances and light."

Theory and practice PDT is a cytotoxic process that depends on the simultaneous presence of a photosensitizing agent, light and oxygen to effectively treat a variety of dermatologic conditions. In a classic setting, treating actinic keratoses, the physician administers large concentrations of topical 5-aminolevulinic acid (ALA) on the afternoon prior to PDT treatment.

ALA is a precursor absorbed by the body and converted into a photosensitizer — protoporphyrin IX — that accumulates in abnormal cells.

Thirty minutes of light exposure the following day activates the protoporphyrin IX. That, in turn, causes a release of singlet oxygen molecules that interfere with cellular mitochondria and kill abnormal cells. The patient may feel mild discomfort during treatment. Possible side effects — redness, crusting and a mild peeling — will clear within a few days.

Refining the modality A cosmetic version of the modality would endeavor to optimize aesthetic effects and repair sun-damaged cells.

"Since the idea is photorejuvenation, we may be able to obtain the same effect with different treatment protocols," Dr. Mendes says. "For example, we might be able to lower the concentration of ALA, and instead of waiting 16 hours before light exposure, we are going to see whether a shorter interval — say, one to three hours — will suffice."

The surgeon also plans to test lower light intensities and different sources, such as incoherent light, IPL and red or blue light. In addition to maximizing efficacy, the goal is to make the treatment more convenient, comfortable and cheaper for patients.

Concludes Dr. Mendes, "The beauty is that we have a safe treatment modality, since it uses what is basically a naturally occurring substance. Treatment is confined to superficial layers of the skin, making scarring unlikely. Recovery is well-tolerated and short. Lasers are not necessary. Target areas can be retreated. Additionally, there is the health benefit of treating potentially precancerous lesions, thus conferring a protective effect.

"So, if we have a modality for photorejuvenation that may delay or prevent the appearance of certain skin malignancies, this could be a great thing."

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