Evaluation of the Effectiveness of Imiquimod and 5-Fluorouracil for the Treatment of Actinic Keratosis: Critical Review and Meta-Analysis of Efficacy Studies

Background: Actinic keratosis lesions occur frequently on sun-exposed skin of Caucasians. They become more prevalent with advancing age and are important in identifying the risk factor of those people possibly predisposed to invasive squamous cell carcinoma. Topical therapies are useful alternatives to cryotherapy for treating diffuse actinic damage and a number of preparations have been developed for treating actinic keratosis. Objectives: A cumulative meta-analysis was performed to determine the efficacy of imiquimod 5% cream, which presents a new alternative topical therapy for actinic keratosis, and to compare it to 5-fluorouracil for the treatment of actinic keratosis lesions of the face and scalp. Methods: We searched MEDLINE (1966 to October 2004) for relevant studies evaluating the efficacy of actinic keratosis topical agents imiquimod and 5-fluorouracil (0.5%, 1%, and 5%). Studies included in this meta-analysis required a dosage regimen that was not significantly different from that approved by Health Canada and the U.S. FDA. Studies also required a well-defined treatment duration and followup period, with the primary efficacy variable being the complete (100%) clearance of all actinic keratosis lesions defined as the proportion of patients at followup with no clinically visible lesions in the treatment area. To determine the average efficacy rate for both drugs, the data from each study were combined for that drug. Results: Ten studies were included in the analysis. The average efficacy rate for each drug (with 95% confidence interval) was 5-fluorouracil, 52 ± 18% ( n = 6 studies, 145 subjects) and imiquimod, 70 ± 12% ( n = 4 studies, 393 subjects). Conclusions: The results of this meta-analysis show that both imiquimod and 5-fluorouracil are effective methods for the treatment of actinic keratosis and provide a useful alternative to cryotherapy. However, this analysis suggests that imiquimod may have higher efficacy than 5-fluorouracil for actinic keratosis lesions located on the face and scalp and therefore provides another option to dermatologists.