PD P 506 A-PDT Versus Placebo-PDT and Cryosurgery for the Treatment of AK

Inclusion Criteria: * Written informed consent * Caucasians * Age \> 18 years * Diagnosis of actinic keratosis (AK) with at least four locally separated lesions located on head and/or face (hairless areas) * Selected AK study lesions have clearly defined margins and are mild to moderate (grades I or II) * The distance between the study lesion borders is \> 1.0 cm * Maximum diameter of each study lesion is 1.8 cm * Skin sun sensitivity type I to IV according to Fitzpatrick Exclusion Criteria: * PDT Non-responder * Pre-treatment of the AK lesions eligible for study procedures with pharmaceuticals approved for the treatment of AK during the 4 weeks preceding study treatment * Pre-treatment of the AK lesions eligible for study procedures during the 2 weeks preceding study treatment with keratolytic agents e.g. TCA, urea or salicylic acid containing formulations * Pre-treatment with hypericin during the 2 weeks preceding study therapy * Treatment with systemic retinoids during the 3 months preceding study therapy * Treatment with cytostatics or radiation during the 3 months preceding study therapy * Female patients of childbearing potential * Patients with clinically relevant suppression of the immune system * Diagnosis of Porphyria * Skin diseases that might interfere with response evaluation of study treatment * Skin sun sensitivity type V or VI according to Fitzpatrick * Known intolerance to one or more of the ingredients of the study medication * Known adverse reactions to cryosurgery (including cold urticaria and cold intolerance) * Dementia or psychic condition that might interfere with the ability to understand the study and thus give a written informed consent * Simultaneous participation in another clinical study or participation in another clinical study in the 30 days directly preceding inclusion * Suspected lack of compliance