Comparison of Therapeutic Effect of ALA-PDT with Blue Light According to the Thickness of Atypical Cell Layer and the Histopathologic Subtypes in Actinic Keratosis

Jung, So Young; Hong, Soon Kwon; Seo, Jong Keun; Sung, Ho Suk

Abstract

BACKGROUND
Precancerous diseases of the skin such as actinic keratosis (AK), Bowen disease (BD) and skin cancer, i.e. basal cell carcinoma (BCC), are treated successfully with photodynamic therapy (PDT). In BCC, the therapeutic effect of PDT was different according to the subtypes. However, there has been no study on the response to PDT in the thickness of atypical cell layer and the histopathologic subtype of AK.
OBJECTIVE
We evaluated the responses to PDT using a topical 20% aminolevulinic acid (ALA) solution and a blue light, according to the thickness of atypical cell layer in AK. Further, we assessed the therapeutic response in the histopathologic subtypes of AK.
METHODS
There were a total of 29 AK lesions from 20 patients enrolled in the study. The lesions were incubated with a topical 20% ALA solution for 2 hours and were exposed to blue light (417+/-5 nm) with 10 J/cm2. They were treated 2 times at the 4 weeks intervals. The evaluation of the response to ALA-PDT was done by the skin biopsy at the post 8 weeks period from the last treatment. The therapeutic response was assessed into 3 grades (complete remission, partial remission, no response). The relationship between the therapeutic response and the thickness of atypical cell layer was evaluated. The thickness of atypical cell layer was measured from the most superficial aspect of the Malpighian layer to the tip of rete ridge. In addition, we evaluated the therapeutic effects according to the histopathologic subtypes.
RESULTS
The thickness of atypical cell layer were 0.0327+/-0.0087 mm in complete remission (CR) group, 0.1253+/-0.1128 mm in partial remission (PR) group and 0.1485+/-0.1973 mm in no response (NR) group (p=.0206). CR were achieved in 100% (4/4) of atrophic type, 43.75% (7/16) of hypertrophic type and 0% (0/9) of bowenoid type in AK. The response of ALA-PDT was the best in atrophic type (p=.032) and the lowest in bowenoid type (p=.0051) as compared with other subtypes.
CONCLUSION
The responses to ALA-PDT were different in the thickness of atypical cell layer and it was statistically significant. The therapeutic effect was the best in the atrophic type of AK.