Clinical Question: In patients with actinic keratosis, what are the average progression, regression, and recurrence rates of these skin lesions?
Single actinic keratoses (AKs) progress to squamous cell carcinoma at a rate of 0% to 0.53% per year, whereas regression rates of single AKs ranged from 15% to 63% per year. AK recurrence rates range from 15% to 53%. (LOE = 1b-)
In this systematic review of 24 articles, the authors describe the natural history of AKs: progression to squamous cell carcinoma, regression to healthy skin, or recurrence of the lesions. Because the studies were quite different regarding inclusion criteria, design (both observational and randomized controlled trials), definitions, and follow-up, the authors decided that statistically combining studies was inappropriate. Therefore, they only report the ranges for similar studies and do not perform a meta-analysis. For example, the risk of progression ranged from 0% to 0.53% per lesion for patients both with and without a history of nonmelanoma skin cancer. The authors estimate regression rates of 15% to 63% per lesion, and rates of recurrence range from 15% to 53%. Data describing changes in total AK counts over time vary widely, largely due to underlying differences with regard to sunscreen use or sun avoidance among the patients. In studies where patients were explicitly told to use sunscreen or to avoid the sun, a greater trend toward reduction in total AK count was found, ranging from ?53 to +20%. This study has several limitations that affect its clinical estimates. Many of the articles did not fully report sunscreen use or the impact of age upon lesion behavior. High drop-out rates in some studies, as well as highly variable follow-up rates, also affect the quality of estimates. Several studies did not include information with regard to the treatment performed, especially in situations where squamous cell carcinoma was suspected, and most studies only followed patients for up to 12 months. And, finally, relying on clinical assessments of AK changes or total count can be challenging, particularly in patients with sun-damaged skin. Lauren S. Hughes, MD, MPH Robert Wood Johnson Foundation Clinical Scholar Department of Family Medicine University of Michigan Ann Arbor, MI
Mark H. Ebell, MD, MS
University of Georgia