PDT is underutilized as field treatment for AKs. An expert pushes for two to three hours' incubation time in her clinic and suggests efficacy-elevating pretreatment of lesions.
Despite photodynamic therapy (PDT)'s long history in dermatology, standards remain elusive, and underuse persists, says an expert at the 75th American Academy of Dermatology Annual Meeting, Orlando, Fla.
With PDT, says Nellie Konnikov, M.D., "What we treat on the skin is 50 shades of actinic or solar damage. Actinic keratosis (AK), the disease itself, has different stages and clinical presentations. Dermatologists are very fortunate to have the PDT treatment option in their armamentarium."
She is chief of dermatology, Boston VA Healthcare System, clinical professor of dermatology, Boston University School of Medicine, and adjunct professor of dermatology, Tufts University School of Medicine.
However, she adds, "Phototherapy is underutilized in private practice because people mostly use lesion-specific therapies or spot therapies for what we see on the skin."
Approved by the U.S. Food and Drug Administration (FDA) for more than 10 years, "Phototherapy treats the entire area of potential or probable damage - not only lesions that we can see with the naked eye or feel with our fingertips," she says.
Field therapy addresses the cellular level, she says, for medical and aesthetic indications ranging from prophylaxis of precancerous lesions to improving skin texture, quality and color.
In many states, physicians can delegate the procedure.
"It's cost-effective for our practice. I practice in an academic environment where dermatology residents from Boston University, Tufts University and Harvard Medical School come to learn with us. All of them get hands-on experience in PDT. This prepares them for practice, by counseling patients on benefits of PDT and following them post-procedure," she says.
PDT is especially beneficial for elderly patients, Dr. Konnikov says, because it eliminates the need to return every few months for spot treatments of AKs.
"It's usually well-tolerated. Sometimes we do two sessions in a row," separated by one to two months, then a follow-up visit one year later. "This is the very same cohort of patients we used to see every 2 to 3 months for spot cryotherapy,” she notes.
In practice, most physicians use shorter incubation times than were initially approved.
"It's a standard of care and a matter of preference. The photosensitizer, aminolevulinic acid, that needs to react with the light source, starts accumulating in the cells within an hour. How much must accumulate to be effective? This is changing turf" One to 1.5 hours incubation is probably sufficient,1 she says.
"In our clinic, we'll push for two to three hours because we believe that will improve efficacy, although studies have not yet shown this. We give the patient some latitude," allowing for 1.5 to three hours' incubation.
"I wouldn't go less than one hour because the accumulation is negligible. More than a decade ago, we showed that short incubation can provide significant textural effects, cosmetic results and reduction in AKs," she says.
To use PDT correctly, "The light source must be blue or red." In Europe, she adds, daytime PDT - where patients are instructed to simply go outside and get a few daylight hours of UV exposure - is gaining popularity.
"It seems to be very well-tolerated and less painful for the patient. But there are no well-controlled studies in the United States – case reports have mostly been published in European literature." Dr. Konnikov says that presently, due to concerns for phototoxicity and legal liability, "I wouldn't use daytime photodynamic therapy within our VA practice." To avoid phototoxicity, patients must be very clearly instructed to avoid sunlight for 24 to 36 hours after treatment.
Above all, she says, "Photodynamic therapy is not a cure. It's a very good treatment option in our armamentarium for numerous, multiple AKs, visible or otherwise."
To boost its efficacy, she suggested pretreating the desired area with 5-fluorouracil cream for one week.
"Another option is to pretreat hyperkeratotic lesions." To help the photosensitizer penetrate, Dr. Konnikov suggests mechanically removing the hyperkeratosis with an instrument such as a curette.
"Otherwise, the efficacy drops significantly. And then the 'failure' is not a failure of this particular treatment – it's a failure to prepare the skin properly," she says
Disclosures: Dr. Konnikov is a member of the scientific board of Biofrontera.
1. Touma D, Yaar M, Whitehead S, Konnikov N, Gilchrest BA. A trial of short incubation, broad-area photodynamic therapy for facial actinic keratoses and diffuse photodamage. Arch Dermatol. 2004;140(1):33-40.