Faculty Bibliography

BACKGROUND: The rates of short-term clearance of actinic keratoses appear to be comparable in clinical trials of topical treatments used in field therapy, but direct comparisons of efficacy results can be problematic. Trials use different efficacy end points, have different study designs, involve different anatomic sites, and enroll different patient populations. In addition, because adherence in real-world clinical practice differs from that observed in clinical trials, conclusions drawn from efficacy outcomes can be misleading. The objective of this review was to examine the efficacy end points used in studies of topical therapy for actinic keratosis, address other factors influencing efficacy outcomes in these studies, and discuss the possible influence of nonadherence on effectiveness. METHODS: Review of the available literature on topical therapy for actinic keratosis. RESULTS: The end points used to determine efficacy of therapies for actinic keratosis include a disparate group of outcomes, which can often make comparison between studies impossible. CONCLUSIONS: Efficacy end points of clinical studies designed to assess the treatment of actinic keratosis should be standardized to facilitate between-trial comparisons, and studies should focus on the end points that are most clinically relevant.

Chronic, long-term sun exposure results in genetic changes in epidermal keratinocytes and the development of various skin lesions ranging from actinic keratosis (AK) to skin cancer. AK lesions may first appear as rough, scaly spots on sun-exposed skin, and, although most individual AK lesions do not become invasive cancers, the majority of invasive squamous cell carcinomas originate from AK. Genetic analysis demonstrates that ultraviolet radiation-induced mutations and changes in gene expression are present in squamous cell carcinoma, AK, and clinically normal-appearing perilesional sun-exposed skin, which supports the progressive nature of keratinocyte transformation. The presence of certain clinical features, such as large size, ulceration, or bleeding, suggests an increased risk of disease progression. The risk is also increased by evidence of extensive solar damage, advanced age, and immunosuppression. Early diagnosis and consideration for treatment are indicated to clear actinically damaged sites and diminish the risk of invasive squamous cell carcinoma.

BACKGROUND: The manner in which consumers apply sunscreens is often inadequate for ultraviolet protection according to the labeled sun protection factor (SPF). Although sunscreen SPFs are labeled by testing at an application density of 2 mg/cm(2), the actual protection received is often substantially less because of consumer application densities ranging from 0.5 to 1 mg/cm(2). High-SPF sunscreens may provide more adequate protection even when applied by consumers at inadequate amounts. OBJECTIVE: We sought to measure the actual SPF values of various sunscreens (labeled SPF 30-100) applied in amounts typical of those used by consumers. METHODS: Actual SPF values were measured on human volunteers for 6 sunscreen products with labeled SPF values ranging from 30 to 100, applied at 0.5, 1.0, 1.5, and 2.0 mg/cm(2). RESULTS: There was a linear relationship between application density and the actual SPF; sunscreens with labeled SPF values of 70 and above provided significant protection, even at the low application densities typically applied by consumers. Sunscreens labeled SPF 70 and 100 applied at 0.5 mg/cm(2) provided an actual SPF value of, respectively, 19 and 27. LIMITATIONS: The study was conducted in a laboratory setting under standardized conditions and results are extrapolated to actual in-use situations. CONCLUSION: Sunscreens with SPF 70 and above add additional clinical benefits when applied by consumers at typically used amounts, by delivering an actual SPF that meets the minimum SPF levels recommended for skin cancer and photodamage prevention. In contrast, sunscreens with SPF 30 or 50 may not produce sufficient protection at actual consumer usage levels.

Melanoma is an important public health problem in the United States and worldwide. The incidence of melanoma continues to increase at a high rate and deaths from melanoma are also increasing. The endogenous risk factors that are currently recognized are in many cases surrogates for genetic markers yet to be determined. Exogenous risk factors need to be better defined and understood to help develop better public education programs that can change risk behaviors and subsequently lower future incidence and mortality from melanoma.

Total cumulative sun exposure is associated with the development of squamous cell and basal cell cancers, whereas intense intermittent sun exposure is associated with the development of melanoma. Exposure to UV radiation is the only known modifiable cause of melanoma, but the role of sunscreen in melanoma prevention remains somewhat controversial. This article discusses how UV radiation contributes to the pathogenesis of melanoma, how sunscreen modulates the action of UV radiation on the skin, and the effect of sunscreen on the risk of developing melanoma. A review of available sunscreen agents and their sun-protective properties is also included.