Treatment of precancers with topical agents

Actinic keratosis (AK), also termed solar keratosis and senile keratosis, is a very common lesion of the skin and is a potential precursor to squamous cell carcinoma (SCC). Estimates of AK progression to invasive SCC range from less than 1 to 16% [1]. SCC of the skin has the potential to metastasize and may account for up to 20% of deaths from skin cancer [2]. With the incidence of nonmelanoma skin cancer on the rise, treatment for AKs has been recommended to reduce the development of invasive SCC, to lower healthcare expenditure, and for patient well-being [3, 4]. The likelihood of an invasive SCC evolving from one AK lesion has been estimated to occur at a rate of 0.075–0.096% per lesion per year. For a person with the average number of AKs, or 7.7 AKs, SCC would develop at a rate of 10.2% over 10 years. Other estimates quote even higher rates for untreated lesions, from 13 to 20% over a 10-year period [4].