Impact of light dose and fluence rate on the efficacy and tolerability of topical 5-ALA photodynamic therapy for actinic keratoses: A randomized, controlled, observer-blinded intrapatient comparison study.

Background: Conventional photodynamic therapy (cPDT) is an effective treatment option for field cancerization and multiple actinic keratoses (AK). The main side effect of cPDT is pain during illumination which in severe cases might necessitate early termination of treatment. Modification of treatment parameters such as light dose and fluence rate is a promising approach to mitigate PDT-associated pain.

Objectives: The aim of this study was to compare the efficacy and tolerability of four different cPDT illumination protocols in the treatment of AK in the head region.

Methods: Prospective, investigator-blinded, within-patient study on 67 patients with multiple AK in the head region. PDT treatment was performed on comparable target areas with four different settings of illumination: (A) standard light dose and standard fluence rate, (B) standard light dose and halved fluence rate, (C) halved standard light dose and standard fluence rate and (D) halved standard light dose and halved fluence rate. Pain and the intensity of the phototoxic skin reaction was recorded during and after illumination. The clearance rate of the target areas and target lesions was assessed at 12 weeks after PDT. Target areas with incomplete clearance were retreated, those with complete clearance were reassessed at 24 weeks after PDT.

Results: The mean and maximum pain level during illumination was significantly decreased at the lower fluence rates. The phototoxic skin reaction was most pronounced with the standard illumination setting. The overall clearance rate of AK and the clearance rate of the target lesions at 3 months after PDT as well as the number of recurrent or new AK at 6 months after PDT did not differ between four treatment protocols.

Conclusions: Reduction of the fluence rate and/or light dose was associated with less PDT-induced pain and/or shorter exposures times without compromising the therapeutic efficacy of cPDT for AK in the head region.