Effects of Topical Diclofenac on Tumor Metabolism

Inclusion Criteria: * Written informed consent has been signed prior to or at Screening Visit * Caucasian male and female patients * Age \> 18 years * Negative pregnancy test in women of childbearing age * Clinical diagnosis of actinic keratosis (AK) * A minimum of three AK lesions Exclusion Criteria in immunocompromised patients : * Concomitant UV-phototherapy * Pregnancy or lactation * Women in child-bearing age who do not use highly efficient contraceptive methods (\<1% failure rate per year) * Skin diseases that might interfere with response evaluation of study treatment * Topical pretreatment of the AK study lesions with photodynamic therapy, Solaraze® 3% gel, Aldara®, 5-FU, or polyphenon E during the 8 weeks preceding study treatment * Radiation therapy performed in the treatment area during the 3 months preceding study therapy * Systemic treatment with diclofenac * Known intolerance to diclofenac or to any other ingredient of Solaraze® 3% gel * Conditions that might interfere with the ability to understand the study and thus give 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 Exclusion criteria in immunocompetent patients: * Concomitant UV-phototherapy * Pregnancy or lactation * Women in child-bearing age who do not use highly efficient contraceptive methods (\<1% failure rate per year) * Patients with clinically relevant suppression of the immune system (e.g. drug induced, infection) * Skin diseases that might interfere with response evaluation of study treatment * Topical pretreatment of the AK study lesions with photodynamic therapy, Aldara®, Solaraze® 3% gel , 5-FU, or polyphenon E during the 8 weeks preceding study treatment * Systemic treatment with cytostatic drugs or radiation therapy performed in the treatment area during the 3 months preceding study therapy * Systemic treatment with diclofenac * Known intolerance to diclofenac or to any other ingredient of Solaraze® 3% gel * Conditions that might interfere with the ability to understand the study and thus give written informed consent * Simultaneous participation in another clinical study or participation in another clinical study in participation in another clinical study in the 30 days directly preceding inclusion * Suspected lack of compliance