Sunscreen Use and Ultraviolet (UV) Radiation Avoidance
The evidence that interventions designed to reduce exposure to UV radiation by the use of sunscreen, protective clothing, or limitation of sun exposure time decrease the incidence of nonmelanoma skin cancer is inadequate. A randomized study suggested a possible reduction in incidence of squamous cell carcinomas (SCCs), but study design and analysis problems complicate interpretation of the results.[1,2]
Squamous cell carcinoma (SCC) (together with BCC referred to as nonmelanoma skin cancer [NMSC]).
BCC and SCC are the most common forms of skin cancer but have substantially better prognoses than the less common, generally more aggressive, melanoma.
NMSC is the most commonly occurring cancer in the United States. Its incidence appears to be increasing in some, but not all, areas of the country. Overall U.S. incidence rates have likely been increasing for a number of years. At least some of this increase may be attributable to increasing skin cancer awareness and resulting increasing investigation and biopsy of skin lesions. The total number and incidence rate of NMSCs cannot be estimated precisely, because reporting to cancer registries is not required. However, based on extrapolation of Medicare fee-for-service data to the U.S. population, it has been estimated that the total number of persons treated for NMSCs in 2006 was about 2,152,500. That number exceeds all other cases of cancer estimated by the American Cancer Society for that year, which was about 1.4 million.
Melanoma is a reportable cancer in U.S. cancer registries, so there are more reliable estimates of incidence than is the case with NMSCs. In 2011, it is estimated that 70,230 individuals in the United States will be diagnosed with melanoma and approximately 8,790 will die of the disease.
The incidence of melanoma has been increasing for at least 30 years.
Epidemiologic evidence suggests that exposure to UV radiation and the sensitivity of an individual's skin to UV radiation are risk factors for skin cancer, though the type of exposure (high-intensity and short-duration vs. chronic exposure) and the pattern of exposure (continuous vs. intermittent) may differ among the three main skin cancer types.[6,7,8] In addition, the immune system may play a role in pathogenesis of skin cancer. Organ transplant recipients receiving immunosuppressive drugs are at an elevated risk of skin cancer, particularly SCC. Arsenic exposure also increases the risk of cutaneous SCC.[9,10]
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.