Thicker AK lesions benefit from laser pretreatment with high channel density

Photodynamic therapy (PDT) is an approved treatment of actinic keratosis (AK). A study showed that ablative fractional laser pretreatment can enhance its efficacy: a high laser channel density should be chosen in patients with hyperkeratotic lesions [1].

AK is an intraepidermal proliferation of dysplastic keratinocytes that develops in response to chronic exposure to UV radiation. There are numerous treatment methods. One of the most effective is PDT, which involves the use of a topical photosensitising agent such as methyl aminolevulinate (MAL) before exposure to an activating light source to generate reactive oxygen species that lead to cell death. However, stratum corneum is a major barrier for drug permeation, thus decreasing transdermal MAL uptake. Therefore, different pretreatment options have been assessed to enhance PDT efficacy, including microdermabrasion, microneedling, and ablative fractional laser pretreatment. The latter has been shown in a previous study to be effective in enhancing the penetration and accumulation of photosensitisers [2].

In the present study, Dr Yeo-Rye Cho (Dong-A University Busan, Korea) and her colleagues assessed whether there are differences dependent on the chosen laser channel density of the microscopic ablation zones. Korean patients (n=47) with 312 AK lesions were enrolled in the study and treated with 5.5% ablative fractional laser (AFL)-PDT, 11% AFL-PDT, or 22% AFL-PDT and received 1 session of PDT after AFL therapy. Treatment efficacy was determined based on the regression of lesions over time; and accumulated levels of bioconversion to protoporphyrin IX (PpIX), side effects, and cosmetic outcomes were assessed.

Higher channel density associated with higher response rates

No difference was observed in the protoporphyrin IX accumulation between the different groups. "Obviously, the lowest channel density was sufficient to achieve maximum drug penetration," said Dr Cho. However, a significant difference between the complete response rate at 3 months, and in particular at 12 months were noted. After a year, 60.9% of the patient in the 5.5% group compared with 74.0% in the 11% group, and 81.1% in the 22% group showed a complete response (P=0.003). Most benefits were noticed in patients with Olsen grade III lesions, a score for AK that grades severity/thickness of individual AK lesions. After 12 months, 38.2% in the 5.5% group compared with 57.1% in the 11% group and 68.8% in the 22.0% group showed a complete response (P=0.043). “Patients with thick lesions seem to benefit most from the 22% density as the debulking effect is more pronounced,” said Dr Cho. There were no differences with regard to side effects; rates of erythema were similar in all 3 groups. In addition, the cosmetic effect was comparable. There were no differences with regard to side effects; rates of erythema were similar in all three groups. In addition, the cosmetic effect was comparable.

"As AK with severe hyperkeratosis showed a better long-term complete response rate with lesser recurrences, we recommend AFL with higher laser channel density when AFL-PDT is used to treat AK with severe hyperkeratosis," concluded Dr Cho.

1. Cho Y-R. Abstract 11263, AAD Annual Meeting, 1-5 March 2019, Washington DC, USA.
2. Ko DY, et al. J Eur Acad Dermatol Venereol 2014;28:1529-39.



Posted on 19 April 20195 September 2024