The risk of progression to invasive disease

Actinic keratoses occasionally progress to invasive skin cancer. The clinician-dermatologist ideally would like to know which lesions are at individual risk. Various investigators have attempted to answer this problem through a variety of clinical research applications including counting individual lesions in populations at risk, in the general population, and by examining insurance claims data and extrapolating incidence figures.

The purpose of the study was to ascertain the range of risks for progression of actinic keratoses to invasive skin cancer.

Five clinical research studies were reviewed that covered a period from 1988 to 1998. Published risk of progression of actinic keratoses to invasive squamous cell carcinoma for individual lesions ranged from 0.025% to 16% per year. Extrapolation from these clinical studies suggests a rate of risk of progression of actinic keratoses to invasive squamous cell carcinoma of approximately 8% taken as an average among the cited statistical rates in the studies reviewed.

Although the rate of progression of actinic keratoses to invasive squamous cell carcinoma statistically occurs at a low percentage rate ( approximately 10%), the problem for the clinician is that the risk over a broad population does not aid in determining the risk factor for the individual lesion. Hence the decision to treat is made on related clinical factors such as history of persistence, age of patient, discomfort, extent of coexisting photodamage, tolerance for morbidity of therapy, and history of skin cancer.