Long‐term follow‐up of a randomized, double‐blind, phase III, multi‐centre study to evaluate the safety and efficacy of field‐directed photodynamic therapy (PDT) of mild to moderate actinic keratosis using BF‐200 ALA versus placebo and the BF‐RhodoLED® lamp

In actinic keratosis (AK), field cancerization describes areas of skin where multiple visible AK lesions are surrounded by healthy looking skin containing non-visible (subclinical) lesions. As all AK lesions have a risk of progression to cutaneous squamous cell carcinoma, experts advise field-directed treatment. Photodynamic therapy (PDT) is an effective field-directed treatment option for AK; however, long-term efficacy data are still scarce.