The impact of occlusive vs non-occlusive application of 5-aminolevulinic acid (BF-200 ALA) on the efficacy and tolerability of photodynamic therapy for actinic keratosis on the scalp and face: A prospective within-patient comparison trial

Background Photodynamic therapy (PDT) is an effective treatment for actinic keratoses (AK). PDT is usually performed with occlusion of the photosensitizer prior to subsequent illumination. Objectives This study aimed to compare the efficacy and tolerability of occlusive versus non-occlusive application of a 5-aminolevulinic gel (BT-200 ALA) for PDT of multiple AK on the scalp or face. Methods Prospective, investigator-blinded, within-patient comparison study on 45 patients. PDT with occlusion of ALA was performed in a target area on one randomized side of the scalp or face. One week later a contralateral target area received the same treatment except that no occlusion of the ALA gel was performed. 3 and 6 months after PDT, the clearance rate of a predetermined target lesion and the total clearance rate of all AK within the treated areas were determined. PDT-induced pain and skin phototoxicity and cosmetic outcome were also recorded. Results Clearance rate of the target AK and total AK clearance rate at 3 months after PDT was 88.4% and 90.6% for occlusive PDT and 58.1% (P = .001) and 70.4% (P = .04) for non-occlusive PDT. The corresponding values at 6 months after PDT were 69.7% and 72.1% for occlusive PDT and 30.2% (P < .001) and 35.6% (P = .001) for non-occlusive PDT. Pain score and skin phototoxicity were significantly higher after occlusive ALA application. No difference was observed with respect to cosmetic outcome. Conclusions Occlusive application of ALA significantly improves the efficacy of PDT but is associated with more pain and increased phototoxicity.