摘要： Photodynamic therapy (PDT) with methyl aminolevulinate (MAL) is effective in the treatment of actinic keratosis (AK). Protoporphyrin IX (PpIX) transformed from MAL is accumulated in abnormal AK cells, which are destroyed by light irradiation during PDT. However, AK hyperkeratosis is known to reduce the PDT treatment response, and pretreatment with ablative fractional laser (AFL) has been successfully used to overcome this barrier. AFL treatment creates microscopic ablation zones (MAZs), allowing easy absorption of MAL and direct evaporation of abnormal cells. We evaluated whether AFL pretreatment with different laser channel densities impacts the efficacy, PpIX accumulation, side effects, and cosmetic outcomes in AFL-PDT for facial AK. This study followed a previous study comparing the efficacy of AFL-PDT according to ablative depth for AK. Patients were randomly assigned to three different AFL density groups with other parameters being fixed. Each lesion was photographed and graded according to Olsen et al. Three hours after MAL application, fluorescence intensity was measured to assess PpIX accumulation and each area was irradiated with a red light-emitting diode lamp (peak emission 630; total light dose 37 J/cm2). Forty-seven Korean patients with 312 AK lesions completed the study (5.5-, 11-, and 22%-density AFL-PDT groups, 16 patients, n=110; 15 patients, n=96; and 16 patients, n=106, respectively). The three groups had no statistical differences in sex, age, Fitzpatrick score, number of lesions, or Olsen grade. However, the complete response (CR) rate was different between the 3 groups at months 3 and 12 (P=0.037; P=0.003, respectively) and the 22%-density AFL-PDT group showed a significantly higher CR rate than the 5.5%-density group (3 months, 88.7% vs. 80.0%; 12 months, 81.1% vs. 60.9%). The CR rate of the different laser densities was investigated for each Olsen grade, and the 22%-density group showed a significantly higher CR rate than the 5.5%-density group (3 months, 81.3% vs. 55.9%; 12 months, 68.8% vs. 38.2%) in Olsen grade III AK lesions. The fluorescence intensities measured and calculated from the photographs were not different among the three groups, and side effects and cosmetic outcomes showed no significant difference. In this study, the CR rate of AFL-PDT was different among the 3 groups, though there were no differences in PpIX accumulation. A recent study also demonstrated that PpIX accumulation showed no difference at laser densities above 5% when AFL is performed in normal skin. However, higher laser density AFL evaporates AK tissues more, and another study showed that AFL treatment temporarily reduced AKs and showed a trend toward decreased development of new lesions. This study had limitations with the small sample size in a single ethnic group, and more studies on AFL-PDT laser density, especially density > 22%, are needed. In conclusion, the group treated with AFL-PDT with higher laser density showed a better CR rate with reduced recurrence, especially for AK with higher Olsen grade. We recommend pretreatment with AFL at a higher laser density when AFL-PDT is used to treat AK with severe hyperkeratosis.