Equivalent efficacy of indoor daylight and lamp‐based 5‐aminolevulinic acid photodynamic therapy for treatment of actinic keratosis

BACKGROUND: Photodynamic therapy (PDT) is widely used as a treatment for actinic keratoses (AK), with new sunlight‐based regimens proposed as alternatives to lamp‐based treatments. Prescribing indoor daylight activation could help address the seasonal temperature, clinical supervision, and access variability associated with outdoor treatments. OBJECTIVE: To compare the AK lesion clearance efficacy of indoor daylight PDT treatment (30 min of 5‐aminolevulinic acid (ALA) pre‐incubation, followed by 2 h of indoor sunlight) versus a lamp‐based PDT treatment (30 min of ALA preincubation, followed by 10 min of red light). METHODS: A prospective clinical trial was conducted with 41 patients. Topical 10% ALA was applied to the entire treatment site (face, forehead, scalp). Patients were assigned to either the lamp‐based or indoor daylight treatment. Actinic keratosis lesion counts were determined by clinical examination and recorded for pre‐treatment, 1‐month, and 6‐month follow‐up visits. RESULTS: There was no statistical difference in the efficacy of AK lesion clearance between the red‐lamp (1‐month clearance = 57 ± 17%, 6‐month clearance = 57 ± 20%) and indoor daylight treatment (1‐month clearance = 61 ± 19%, 6‐month clearance = 67 ± 20%). A 95% confidence interval of the difference of the means was measured between −4.4% and 13.4% for 1‐month, and −2.2% and +23.6% for 6‐month timepoints when comparing the indoor daylight to the red‐lamp treatment, with a priori interval of equivalence of ±20%. LIMITATIONS: Ensuring an equivalent dose between the indoor and lamp treatment cohorts limited randomisation since it required performing indoor daylight treatments only during sunny days. CONCLUSION: Indoor‐daylight PDT provided equivalent AK treatment efficacy to a lamp‐based regimen while overcoming temperature limitations and UV‐block sunscreen issues associated with outdoor sunlight treatments in the winter. CLINICAL TRIAL REGISTRATION: Clinicaltrials.gov listing: NCT03805737.