Daylight PDT for Actinic Keratoses: a Multicentre Study Comparing Two Photosensitizers (BF-200 ALA Versus MAL)

Overview

This study compares two photosensitizing creams' BF-200 ALA's (aminolevulinic acid, Ameluz®) and MAL's (methyl 5-aminolevulinate, Metvix®) efficacy on actinic keratoses in natural daylight photodynamic therapy (NDL-PDT). The participants' facial skin or scalp will be randomized in two sides and one side is treated with BF-200 ALA and the other side with MAL. Result of the treatment is assessed with clinical examination 12 months after treatment. The investigators will also compare delayed skin reactions after treatment and cost-effectiveness of both photosensitizer creams.

Photodynamic therapy (PDT) is a widely used method in dermatology clinics for treatment of superficial skin cancers and premalignant lesions. Actinic keratoses (AKs) are premalignant skin lesions which develop due to long-lasting sun exposure and in time can progress into squamocellular skin cancer if left untreated. The incidence of AKs and skin cancers is rapidly booming as the elderly population increases in western countries. It is crucial to treat AKs early and effectively considering their tendency to progress into malign cancer. The current general consensus for treating AKs is to treat large sun-damaged skin areas simultaneously instead of separate AK lesions. Term "skin field cancerization" refers to presence of different degrees of visible and invisible dysplastic changes in widely sun-damaged skin. Natural daylight mediated photodynamic therapy (NDL-PDT) is a well-suited method for treating large field-cancerized skin areas. In PDT a photosensitizing cream is applied on the skin and let to absorb. After absorption to the skin cells the photosensitizer changes into protoporphyrin IX (PpIX). PpIX reacts with visible light causing a phototoxic reaction which destroys cancer cells targetedly. After absorption the skin can be illuminated using a red lamp (conventional PDT) or natural daylight (NDL-PDT) as the absorption spectrum peaks of PpIX are within the visual spectrum of light. In Finland the approved photosensitizers for PDT are methyl 5-aminolevulinate cream (MAL, Metvix®, Galderma) and aminolevulinic acid gel (BF-200 ALA, Ameluz®, Biofrontera AG). They both have been clinically studied and proved effective in conventional PDT but in NDL-PDT mainly MAL has been in focus of studies. To our knowledge there is only research report concerning the use of BF-200 ALA in NDL-PDT (Neittaanmaki-Perttu et al 2014) which is a study of our own research group. In this study BF-200 ALA appeared to be more effective than MAL.