Microneedles poised to become increasingly valuable clinically
ORLANDO –
Dr. Spencer, who practices in St. Petersburg, Fla., and is cochair of the conference, gave attendees a roundup of what’s new in adjuncts and delivery methods for photodynamic therapy (PDT). Among the updates is the promise of PDT delivered by means of an ultrashort incubation time of 10-20 minutes, followed by prolonged blue light exposure time of 1 hour. “The idea is that the enzymatic conversion is occurring during the light exposure,” Dr. Spencer said, adding that reports of this approach are mostly anecdotal.
A variation on the ultrashort incubation adds microneedling, he said. In one recent study, 33 patients who had facial actinic keratoses (AKs) were randomized to 10 or 20 minutes of incubation after application of aminolevulinic acid (ALA), followed by 1,000 seconds of exposure to blue light. However, in this split-face study, participants each had one side of their faces treated with microneedling and the other half with a sham treatment before ALA was applied.
Those who had the shorter incubation time had 43% of AKs cleared on the side that received microneedling, compared with 38% on the sham side. For those who received 20 minutes of ALA incubation, rates were higher, with 76% AK clearance on the treated side and 58% on the sham side. “Patients reported that the procedure was virtually painless on both sides,” said Dr. Spencer.
Though the addition of microneedling to PDT is a newer trend, there’s one that’s been a mainstay in Europe for some time: daylight PDT. He cited a review article published in 2016, which identified 17 studies on the use of daylight PDT (Dermatol Surg. 2016 Mar;42[3]:286-95).
Advantages of daylight PDT, he said, include less time in the office for patients and “supposedly less pain.” European protocols vary, but most use methyl aminolevulinate, which he said is a “little more lipophilic than ALA,” with incubation times ranging from 0 to 30 minutes. Exposure time is also variable, but will usually range from 1.5 to 2.5 hours. Most patients receive just one treatment, but some protocols will include up to three treatments.
Overall, studies show a range from 46% to almost 90% complete response rates when AKs are treated with daylight PDT. One study that looked at daylight PDT for small basal cell carcinomas showed that 94% of patients had clinical clearance of their lesions after two treatment sessions; however, the recurrence rate at 12 months post therapy was 21%, Dr. Spencer said.
He shared results of a recent head-to-head study of conventional and daylight PDT; conducted in Greece, the study enrolled patients with “high sun exposure” and used a split-face design.
Of the 46 patients who received MAL on both sides of their faces, response rates were similar at both 3 and 12 months, with slightly numerically higher clearance rates for conventional versus daylight PDT. The 3-month clearance rate for conventional PDT was 80.6%, compared with 78.0% for daylight PDT. At 12 months, the respective clearance rates were 73.7% and 71.8% (J Eur Acad Dermatol Venereol. 2018 Apr;32[4]:595-600). However, “significantly less pain was reported with daylight PDT,” Dr. Spencer said.
Daylight PDT hasn’t caught on the United States. Physicians have concern about the lack of control of UV dosing, and, he pointed out, “this, of course, is not billable.”
Dr. Spencer reported that he serves on the speakers bureau for Genentech.