• actinic keratoses;
  • methyl aminolevulinate;
  • photodynamic therapy;
  • short incubation


Background  Photodynamic therapy (PDT) using methyl aminolevulinate (MAL) is an effective first-line treatment for actinic keratoses. A reduced incubation period may have practical advantages.

Objective  This study aims to evaluate the effect of incubation time (1 vs. 3 h), MAL concentration (160 mg/g vs. 80 mg/g) and lesion preparation in the setting of MAL-PDT for treatment of actinic keratosis (AK).

Design  Open, randomized, parallel-group multicentre study.

Setting  Outpatient dermatology clinics.

Subjects  One hundred and twelve patients with 384 previously untreated AK. Most lesions (87%) were located on the face and scalp and were thin (55%) or moderately thick (34%).

Methods  Lesions were debrided, and MAL cream (160 mg/g or 80 mg/g) was applied before illumination with red light (570–670 nm; light dose, 75 J/cm2). Patients were followed up at 2 and 3 months. Sixty patients (54%) were re-treated and assessed at 6 months.

Main outcome  Complete lesion response rates 3 and 12 months after last treatment.

Results  For lesions on the face/scalp, lesion complete response rates were 78% for thin AK and 74% for moderately thick AK lesions after 1 h vs. 96% and 87% after 3 h incubation with MAL 160 mg/g. Lesion recurrence rates at 12 months after two treatments were similar [19% (3 of 16) with 1 h vs. 17% (3 of 18) with 3 h 160 mg/kg MAL-PDT] and lower than for 80 mg/g MAL-PDT (44–45%).

Conclusion  MAL-PDT using a 1-h incubation may be sufficient for successful treatment of selected AK lesions.

Conflicts of interest

Lasse R Braathen consults for Photocure and has received speaker honoraria from Photocure and Galderma. Trond Warloe is a co-inventor of the corresponding patent and is a minor share holder of Photocure ASA. Tore Morken has been paid as a chairman of a Photocure-sponsored symposium. Bruno E Paredes, Olli Saksela, Clemens Fritsch, Kerstin Gardlo, Karin W Frölich, Ana M Solér and Ann-Marie Ros do not have any relevant conflict of interest, financial or otherwise.