Description of the Evidence
The visible evidence of susceptibility to skin cancer (skin type and precancerous lesions), of sun-induced skin damage (sunburn and solar keratoses), and the ability of an individual to modify sun exposure provide the basis for implementation of programs for the primary prevention of skin cancer.
Factors associated with increased risk of nonmelanoma skin cancer
Ultraviolet (UV) radiation exposure
Most evidence about UV radiation exposure and the prevention of skin cancer comes from observational and analytic epidemiologic studies. Such studies have consistently shown that increased cumulative sun exposure is a risk factor for NMSC.[7,8] Individuals whose skin tans poorly or burns easily after sun exposure are particularly susceptible.
Factors associated with an increased risk of melanoma
UV radiation exposure
The relationship between UV radiation exposure and cutaneous melanoma is less clear than the relationship between UV exposure and NMSC. In the case of melanoma, it seems that intermittent acute sun exposure leading to sunburn is more important than cumulative sun exposure; such exposures during childhood or adolescence may be particularly important.
Interventions With Inadequate Evidence as to Whether They Reduce Risk of Nonmelanoma Skin Cancer
Sunscreen use and UV radiation avoidance
It is not known if interventions designed to reduce exposure to UV radiation through the use of sunscreens and/or protective clothing or through limitation of exposure time reduce the incidence of NMSC in humans. Some studies have used solar keratoses rather than invasive skin cancer as the study endpoint. It is generally felt that half or more of SCCs arise from solar keratoses. However, nearly half of SCCs occur in clinically normal skin. A longitudinal study has shown that the progression rate from solar keratoses to SCC is about 0.075% to 0.096% per year, or less than 1 in 1,000 per year. Moreover, in a population-based longitudinal study, there was an approximately 26% spontaneous regression rate of solar keratoses within 1 year of a screening examination. Therefore, it is likely that solar keratosis is a poor surrogate endpoint in SCC prevention trials.