Chicago — Along with treating actinic keratoses (AKs), dermatologists are finding photodynamic therapy (PDT) useful for battling other problems including acne and psoriasis, as well as for photorejuvenation.
PDT works by activating a photosensitizing agent, which produces oxygen intermediates that selectively destroy target tissue cells.
"In the early 20th century, PDT was used by several physicians to treat skin cancer. It's much more of an ancient technique than most of us realize," says Kevin S. Pinski, M.D., associate professor of dermatology, Northwestern University.
"When PDT was first being utilized," Dr. Pinski says, "one of the problems was that patients would have to leave the photosensitizer on overnight then come back for treatment. This created logistical problems and the issue of patient discomfort."
In recent years, he says, "investigators have found one can leave the photosensitizer on for 30 minutes to a few hours, and it will work just as well with no discomfort at all, with cure rates up to 90 percent for AKs treated in this fashion (Touma DJ et. al. Lasers Surg Med. 2003;15(S:47).).
"Many physicians will use PDT solely for treatment of AKs. But in my practice, that's one of the minimal usages of it. I find it much more applicable for treatment of many other problems," Dr. Pinski tells Dermatology Times.
Other physicians have used PDT for treating basal cell carcinoma and superficial squamous cell carcinoma in situ (Bowen's disease).
"I don't use PDT as my first-line treatment of choice for these conditions, but it's a potential therapy, especially in nonsurgical candidates or for extensive lesions that are located in difficult areas for cosmetic closures," he says.
Other off-label uses for PDT include acne treatment (Goldman MP, Boyce SM. J Drugs Dermatol. 2003 Aug;2(4):393-396.). This represents the most common PDT application in Dr. Pinski's practice.
"The way I utilize it in my office is with the 5-ALA, leaving it on for anywhere from 30 to 60 minutes in patients and then treating with a blue light for anywhere from eight to 15 minutes," he says.
Typically, Dr. Pinski begins with a conservative treatment time that depends partly on patients' skin sensitivity.
"We tell patients that there are potential side effects," he adds. "The main one is that photosensitivity requires them to limit their outdoor activities for 72 hours. In addition to that, one can still get a little erythema during the first 48 hours post-treatment. But it's usually very minimal and well tolerated."
In moderate inflammatory acne, Dr. Pinski adds, "PDT works wonderfully. I've also treated patients with mild acne and more severe inflammatory acne. I give the typical patient three to four treatments approximately two weeks apart." This regimen typically produces clear skin that can last six to eight months, a duration Dr. Pinski says is typical among practitioners nationwide.
A combined therapy
"PDT is not typically a monotherapy," he cautions. "I will use it in combination with topical treatments or even some systemic antibiotics to eradicate the acne as fast as possible. But PDT certainly allows us to get our patients off of other therapies much faster," a development he considers encouraging in light of problems that have been associated with isotretinoin and overuse of antibiotics.