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Merete Haedersdal, MD, PhD,
On rainy days between October 1 and April 1 in Copenhagen, daylight photodynamic therapy for actinic keratosis is provided to patients in this greenhouse in the garden of Bispebjerg Hospital.
“We have conventional PDT, daylight PDT; we can combine with a range of topicals, and we can combine a range of different physical treatment procedures in order to provide better and individualized treatment regimens for our patients,” Merete Haedersdal, MD, PhD, DMSc, professor of dermatology at the University of Copenhagen, said during a course on laser and aesthetic skin therapy.
In Europe, PDT consists of a three-step procedure: curettage of AKs, application of photosensitizer on the skin (typically methyl aminolevulinate, versus aminolevulinic acid, used more often in the United States), and illumination with red light (versus blue light, used more often in the United States), which causes a photochemical reaction.
“It’s a photochemical-reaction concept with which we can achieve up to 90% cure rates of AKs at 3 months,” Dr. Haedersdal said during the meeting, which was sponsored by Harvard Medical School, Massachusetts General Hospital, and the Wellman Center for Photomedicine.
PDT is also used in Europe for select patients with Bowen’s disease (yielding a 90% cure rate at 3 months, 70% at 2 years); superficial basal cell carcinoma (yielding a 90% cure rate at 3 months, 75% at 5 years), and nodular BCC (yielding a 90% cure rate at 3 months, 75% at 5 years.
“With conventional PDT, whether it’s blue light, red light, MAL, or ALA, we have beautiful cosmesis, but we also have a challenge, which is pain,” she said. This is behind the motivation to look at other ways to provide PDT.
Daylight PDT, which was pioneered by Dr. Haedersdal’s mentor, Hans Christian Wulf, MD, DMSc, PharmD, professor of dermatology at the University of Copenhagen, provides 80%-90% clearance of thin AKs, lower clearance of thick AKs – and is a nearly pain-free procedure because of continuous photoactivation of protoporphyrin IX, with a Visual Analog Scale in the range of 1-3. “Globally, thousands of patients have been treated [with daylight PDT], which is backed up in the literature with more than 150 publications,” she said.
According to Dr. Haedersdal, MAL cream with daylight activation for treatment of AK was approved in Colombia and Mexico in 2013; in Australia, Brazil, and Costa Rica in 2014; and in Chile, Europe, and New Zealand in 2015. “I do hope that one day you will have daylight PDT approved in the United States,” she said.
Dr. Merete Haedersdal
The suggested protocol for daylight PDT starts by applying a sunscreen with an organic filter. After about 15 minutes, the lesion or lesions are prepared, and MAL is applied with no occlusion. Patients should start their exposure to daylight within 30 minutes of application, remaining outdoors for 2 hours of continuous exposure, either at a dedicated space located on the ground of the hospital or clinic or at their home. After 2 hours, patients wipe off the remaining cream and are advised to stay indoors for the rest of the day.
“Ideal candidates are those who have large skin areas that can be easily exposed to sunlight,” such as the scalp and lower legs, said Dr. Haedersdal, who is also a visiting scientist at the Wellman Center for Photomedicine, Boston. “If patients are treated in areas covered by clothing, it can be greasy and sticky with the cream. In these cases, you can cover the area with Tegaderm, which allows for 99% light transmission. Daylight can shine through and the Tegaderm can be removed after the procedure.”
On rainy days between April 1 and October 1 in Copenhagen, she said, daylight PDT is provided in a greenhouse in the hospital garden, with a heater and blankets for patients when the temperature falls below 10° C.
The amount of light required for a treatment effect is 5,000-10,000 lux, and the number of lux on a sunny day in Denmark is about 100,000, she said. “That means that all year round in countries south of latitude 45 degrees N, patients can be treated with daylight PDT.”
To intensify the treatment efficacy of conventional PDT and daylight PDT, especially in those with severely photodamaged skin, combining treatment with a physical pretreatment technique such as curettage, ablative fractional laser, microdermabrasion, microneedling, and nonablative fractional laser is another strategy. A small randomized controlled trial found that ablative fractional laser treatment extended notable relative effectiveness, compared with other physical enhancement techniques.
Dr. Haedersdal and colleagues published a study that compared pretreatment with ablative fractional laser and microdermabrasion pads before daylight PDT for AKs in field-cancerized skin. They found that with a single treatment, combination therapy with ablative fractional laser before daylight PDT led to significantly greater efficacious AK clearance and skin rejuvenation, compared with treatment with microdermabrasion.
“We don’t know why this is, but we believe it may be due to the fact that with the laser, we have a photothermal response, which in combination with the photochemical response from the photodynamic therapy induces a synergistic effect,” she said.
A range of topical treatments can also be given in combination with PDT. In a meta-analysis of 10 randomized controlled trials, German researchers evaluated the efficacy of PDT combined with imiquimod cream, 5-fluorouracil cream, tazarotene gel, and calcipotriol ointment. They concluded that the combination of PDT with another topical drug intervention improves AK clearance rates, compared with monotherapy.
More recently, the same authors summarized the current knowledge on the efficacy and safety of local combination therapies for the treatment of patients with AK in a review article, which Dr. Haedersdal said provides a nice overview of this topic.
Dr. Haedersdal disclosed that she has received equipment from Cherry Imaging, Cynosure-Hologic, MiraDry, and PerfAction Technologies. She has also received research grants from Leo Pharma, Lutronic, Mirai Medical, Novoxel, and Venus Concept.