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 (together with basal cell carcinoma referred to as nonmelanoma skin cancer).
Basal cell carcinoma and squamous cell carcinoma are the most common forms of skin cancer but have substantially better prognoses than the less common, generally more aggressive melanoma.
Nonmelanoma skin cancer is the most commonly occurring cancer in the United States. Its incidence appears to be increasing in some  but not all  areas of the United States. 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. A precise estimate of the total number and incidence rate of nonmelanoma skin cancer is not possible, because reporting to cancer registries is not required. However, based on Medicare fee-for-service data extrapolated to the U.S. population, it has been estimated that the total number of persons treated for nonmelanoma skin cancers in 2006 was about 2,152,500. That number would exceed 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 nonmelanoma skin cancers. 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 it. The incidence of melanoma has been increasing for at least 30 years. Melanoma mortality rates have been decreasing in whites younger than 50 years by 3.0% per year in men since 1991 and by 2.2% per year in women since 1984. However, the rates have been increasing by 1.1% per year since 1989 in white men aged 50 years and older and have been stable since 1990 in white women aged 50 years and older.
A study of skin biopsy rates in relation to melanoma incidence rates obtained from the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute indicated that much of the observed increase in incidence between 1986 and 2001 was confined to local disease and was most likely caused by overdiagnosis as a result of increased skin biopsy rates during this period.
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, although the type of exposure (high-intensity and short-duration vs. chronic exposure) and pattern of exposure (continuous vs. intermittent) may differ among the three main types of skin cancer.[7,8,9] In addition, the immune system may play a role in pathogenesis of skin cancers. Organ-transplant recipients receiving immunosuppressive drugs are at elevated risk of skin cancers, particularly squamous cell cancers (SCC). Arsenic exposure also increases the risk of cutaneous SCC.[10,11]