New study shows success in treating acne with photodynamic therapy
Las Vegas — The most exciting news regarding photodynamic therapy (PDT) involves a new study showing significant results in treating acne, says the study's primary investigator.
"Acne is one of those indications where PDT has been thought about a lot and tried with different combinations of photosensitizers and light sources. Theoretically, it should work," said David M. Pariser, M.D., immediate past-president, American Academy of Dermatology, at the 2012 Fall Clinical Dermatology Conference.
David Pariser, M.D.
However, he adds, previous clinical trials haven't shown that PDT is any more effective than treatment with the light source alone — until now.
In a recently concluded double-blinded, prospective, randomized, vehicle-controlled study, Dr. Pariser and colleagues used methyl aminolevulinate (MAL) and red light in patients with moderate-to-severe acne.
The study included patients with at least 25 inflammatory lesions affecting most of the face. Investigators treated patients with MAL (1.5 hours of incubation) followed by 632 nm red light over four sessions spaced two weeks apart.
At 12 weeks post-treatment, investigators observed a statistically significant and clinically meaningful reduction in inflammatory lesion counts and improvement in investigator global assessment scores, versus control-group patients (unpublished).
Another study has shown PDT with 5-aminolevulinic acid (ALA) and blue light to be effective off-label for actinic keratoses (AKs) on the extremities. Investigators used two treatments spaced eight weeks apart and observed mean lesion count reductions of approximately 58 percent among treated patients versus 25 percent for placebo (Taub AF, Garretson CB. J Drugs Dermatol. 2011;10(9):1049-1056).
ALA vs. MAL
For treating AKs, Dr. Pariser says ALA and MAL are roughly equivalent because these lesions are superficial. However, he says, MAL penetrates more deeply than ALA because it's more lipophilic. Therefore, "It makes a little more sense mechanistically that ALA would work better for acne" and for certain skin cancers.
Blue light is a much more efficient PDT activator than red light, he adds, "But it penetrates only through the dermis and does not reach the deeper structures." This makes red light a better choice for sebaceous glands and skin cancers, Dr. Pariser says.
"The art of PDT requires matching the available science with the type and depth of lesion we want to treat," Dr. Pariser says.
Disclosures: Dr. Pariser's acne study was funded by PhotoCure. Dr. Pariser has been a consultant and investigator for PhotoCure, DUSA and Galderma.
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