A pilot study to assess the efficacy of photodynamic therapy for Japanese patients with actinic keratosis in relation to lesion size and histological severity

Background/purpose: Topical 5‐aminolevulinic acid (ALA)‐based photodynamic therapy (PDT) is effective for actinic keratosis (AK); few studies have examined Oriental patients. The aim of this study is to assess the efficacy of PDT for the treatment of Japanese AK patients classified by lesion size and histological severity. Methods: Thirty patients with solitary AK lesions were divided into two groups according to diameter: a small lesion group (SL), diameter ≤10 mm and a larger lesion group (LL), diameter >10 mm, and histological severity: Group I (mild and moderate) and Group II (severe). After application of 20% ALA for 4 h, exposure to an excimer‐dye laser at 630 nm was performed at a dose of 50 J/cm2 three times at an interval of 7 days. Therapeutic effects were assessed and followed for 12 months. Results: In all 10 SL patients, atypical cells disappeared after PDT and did not recur for 12 months. However, for the 20 LL patients, recurrence was seen in 2 of the 14 Group I patients, while 4 of 6 Group II patients showed residual tumor cells after the first PDT session. Conclusion: The present study demonstrated that ALA‐PDT might be useful for treatment of Japanese AK. The therapeutic outcome might depend on the lesion size and the histopathological severity.